Clarify strings for i18n

lms/templates/instructor/instructor_dashboard_2/extensions.html

@@ -23,11 +23,12 @@
       %endfor
     </select>
   </p>
+  <% format_string="MM/DD/YYYY HH:MM" %>
   <p>
-    ${_("Specify the extension due date and time "
-        "(in UTC; please specify MM/DD/YYYY HH:MM)")}
-    <input type="text" name="due_datetime" 
-           placeholder="MM/DD/YYYY HH:MM"/>
+    ## Translators: "format_string" is the string MM/DD/YYYY HH:MM, as that is the format the system requires.
+    ${_("Specify the extension due date and time (in UTC; please specify {format_string}).").format(format_string=format_string)}</p>
+  <p><input type="text" name="due_datetime" 
+           placeholder="${format_string}"/>
   </p>
   <p class="request-response"></p>
   <p class="request-response-error"></p>
@@ -61,7 +62,7 @@
            data-endpoint="${section_data['show_unit_extensions_url']}">
   </p>
   <p>
-    ${_("Specify a specific student to see all of that student's extensions.")}
+    ${_("Specify a student to see all of that student's extensions.")}
   </p>
   <p>
     ${_("Specify the {platform_name} email address or username of a student "

lms/templates/sysadmin_dashboard.html

@@ -56,6 +56,7 @@ textarea {
 	  <a href="${reverse('sysadmin')}" class="${modeflag.get('users')}">${_('Users')}</a>
       <a href="${reverse('sysadmin_courses')}" class="${modeflag.get('courses')}">${_('Courses')}</a>
       <a href="${reverse('sysadmin_staffing')}" class="${modeflag.get('staffing')}">${_('Staffing and Enrollment')}</a> 
+      ## Translators: refers to http://git-scm.com/docs/git-log
       <a href="${reverse('gitlogs')}">${_('Git Logs')}</a>
     </h2>
 	<hr />
@@ -127,14 +128,14 @@ textarea {
 	<li class="field text">
 	  <label for="repo_location">
 		## Translators: Repo is short for git repository or source of
-		## courseware
+		## courseware; see http://git-scm.com/about
 		${_('Repo Location')}:
 	  </label>
 	  <input type="text" name="repo_location" style="width:60%" />
 	</li>
 	<li class="field text">
 	  <label for="repo_location">
-		## Translators: Repo is short for git repository or source of
+		## Translators: Repo is short for git repository (http://git-scm.com/about) or source of
 		## courseware and branch is a specific version within that repository
 		${_('Repo Branch (optional)')}:
 	  </label>
@@ -142,12 +143,14 @@ textarea {
 	</li>
   </ul>
   <div class="form-actions">
+        ## Translators: Github is a popular website for hosting code
 	<button type="submit" name="action" value="add_course">${_('Load new course from github')}</button>
   </div>
   <hr />
   <ul class="list-input">
 	<li class="field text">
 	  <label for="course_id">
+	        ## Translators: 'dir' is short for 'directory'
 		${_('Course ID or dir')}:
 	  </label>
 	  <input type="text" name="course_id" style="width:60%" />
@@ -210,7 +213,7 @@ textarea {
 %endif
 
   </section>
-  <div style="text-align:right; float: right"><span id="djangopid">${_('Django PID')}: ${djangopid}</span>
+  <div style="text-align:right; float: right"><span id="djangopid">'Django PID': ${djangopid}</span>
   ## Translators: A version number appears after this string
   | <span id="edxver">${_('Platform Version')}: ${edx_platform_version}</span></div>
 </div>

lms/templates/sysadmin_dashboard_gitlogs.html

@@ -55,6 +55,7 @@ textarea {
 	  <a href="${reverse('sysadmin')}">${_('Users')}</a>
       <a href="${reverse('sysadmin_courses')}">${_('Courses')}</a>
       <a href="${reverse('sysadmin_staffing')}">${_('Staffing and Enrollment')}</a> 
+      ## Translators: refers to http://git-scm.com/docs/git-log
       <a href="${reverse('gitlogs')}" class="active-section">${_('Git Logs')}</a>
     </h2>
 	<hr />
@@ -63,6 +64,7 @@ textarea {
     <input type="hidden" name="csrfmiddlewaretoken" value="${ csrf_token }">
     <input type="hidden" name="dash_mode" value="">
 
+      ## Translators: refers to http://git-scm.com/docs/git-log
     <h3>${_('Git Logs')}</h3>
 
 %if course_id is None:
@@ -71,6 +73,7 @@ textarea {
 		<tr>
 		  <th>${_('Date')}</th>
 		  <th>${_('Course ID')}</th>
+		  ## Translators: Git is a version-control system; see http://git-scm.com/about
 		  <th>${_('Git Action')}</th>
 		</tr>
 	  </thead>
@@ -87,6 +90,7 @@ textarea {
 
 %else:
 
+    ## Translators: Git is a version-control system; see http://git-scm.com/about
     <h2>${_('Recent git load activity for')} ${course_id}</h2>
 	%if error_msg:
 	<h3>${_('Error')}:</h3>
@@ -98,7 +102,8 @@ textarea {
 		<tr>
 		  <th>${_('Date')}</th>
 		  <th>${_('Course ID')}</th>
-		  <th>${_('git action')}</th>
+		  ## Translators: Git is a version-control system; see http://git-scm.com/about
+		  <th>${_('Git Action')}</th>
 		</tr>
 	  </thead>
 	  <tbody>

lms/templates/verify_student/midcourse_reverification_confirmation.html

@@ -17,6 +17,7 @@
         <section class="content-confirmation">
           <div class="wrapper-view">
             <div class="view">
+	      ## Translators: 'Credentials' refer to photographs the user has taken to verify their identity.
               <h3 class="title">${_("Your Credentials Have Been Updated")}</h3>
 
               <div class="instruction">