Reverting courseware changes for chat

For embedding chat in a course, user testing shows a course tab is
preferable to the slideout thing, and simpler to implement, so this
commit reverts courseware changes.  Instead, embed chat by creating a
new course tab and setting it's HTML to look like this:

  <iframe src="/courses/COURSE_ID_HERE/chat" width="100%" height="640px"
          style="border: 1px solid #c4bfab; border-radius: 5px;"></iframe>

Conflicts:

	lms/templates/courseware/courseware.html

lms/templates/courseware/courseware.html

 <%inherit file="/main.html" />
 <%namespace name='static' file='/static_content.html'/>
-<%! from django.utils.translation import ugettext as _ %>
-<%! from django.core.urlresolvers import reverse %>
 <%block name="bodyclass">courseware ${course.css_class}</%block>
 <%block name="title"><title>${course.number} Courseware</title></%block>
 
@@ -176,21 +174,6 @@
   </div>
 </section>
 
-% if settings.MITX_FEATURES.get("ENABLE_CHAT") and course.show_chat:
-  <div id="chat-wrapper">
-    <div id="chat-toggle" class="closed">
-      <span id="chat-open">${_("Open Chat")} <em class="icon-chevron-up"></em></span>
-      <span id="chat-close">${_("Close Chat")} <em class="icon-chevron-down"></em></span>
-    </div>
-    <div id="chat-frame-wrapper">
-      ## TODO: this link probably needs course ID as a parameter...
-      <iframe id="chat-block" src="${reverse('chat', kwargs={'course_id': course.id})}"></iframe>
-    </div>
-    <a id="chat-popout" href="#" title="${_('Pop-Out Chat Window')}" class="icon-signout"></a>
-  </div>
-  <a id="chat-popin" href="#" title="${_('Pop-In Chat Window')}" class="icon-signin"></a>
-% endif
-
 % if course.show_calculator:
     <div class="calc-main">
         <a aria-label="Open Calculator" href="#" class="calc">Calculator</a>