Move default Open edX branding into default-theme directory

OPEN-307

lms/djangoapps/branding/__init__.py

@@ -72,6 +72,6 @@ def get_logo_url():
             static_url=settings.STATIC_URL, uni=university
         )
     else:
-        return '{static_url}images/logo-placeholder.png'.format(
+        return '{static_url}images/default-theme/logo.png'.format(
             static_url=settings.STATIC_URL
         )

lms/templates/courseware/courses.html

@@ -22,7 +22,7 @@
       # For some reason, `static.url('images/edx-theme/edx-logo-bw.png')` breaks template rendering.
       default_image_url = settings.STATIC_URL + 'images/edx-theme/edx-logo-bw.png'
     else:
-      default_image_url = settings.STATIC_URL + 'images/logo-placeholder-large.png'
+      default_image_url = settings.STATIC_URL + 'images/default-theme/logo-large.png'
 
     logo_file = microsite.get_value(
       'course_index_overlay_logo_file', default_image_url

lms/templates/footer.html

@@ -45,8 +45,8 @@
         <p>
           <a href="/">
             ## this is just a placeholder logo
-            ## feel free to change this logo to your own
-            <img alt="organization logo placeholder" src="/static/images/logo-placeholder.png">
+            ## feel free to change this logo to your own by replacing "logo.png" with your own logo
+            <img alt="organization logo placeholder" src="/static/images/default-theme/logo.png">
           </a>
         </p>
       </div>