Swap out the homepage and courses banner image for something school-neutral (this is temporary)

lms/static/sass/_course_about.scss

@@ -5,7 +5,7 @@
 
   header.course-profile {
     background: rgb(245,245,245);
-    @include background-image(url('/static/images/shot-2-large.jpg'));
+    @include background-image(url('/static/images/homepage_interns_placeholder_2025x550.jpg'));
     background-size: cover;
     @include box-shadow(0 1px 80px 0 rgba(0,0,0, 0.5));
     border-bottom: 1px solid rgb(100,100,100);

lms/static/sass/_home.scss

@@ -3,7 +3,7 @@
 
   > header {
     background: rgb(255,255,255);
-    @include background-image(url('/static/images/shot-2-large.jpg'));
+    @include background-image(url('/static/images/homepage_interns_placeholder_2025x550.jpg'));
     background-size: cover;
     border-bottom: 1px solid rgb(80,80,80);
     @include box-shadow(0 1px 0 0 rgba(255,255,255, 0.9), inset 0 -1px 5px 0 rgba(0,0,0, 0.1));

lms/templates/courses.html

@@ -3,7 +3,7 @@
 <%namespace name='static' file='static_content.html'/>
 
 <section class="find-courses">
-  <header class="search" style="background: url('/static/images/shot-2-large.jpg')">
+  <header class="search" style="background: url('/static/images/homepage_interns_placeholder_2025x550.jpg')">
     <div class="inner-wrapper main-search">
       <hgroup>
         <div class="logo">