Theme static error pages

Reference the `PLATFORM_NAME` and `TECH_SUPPORT_EMAIL` settings in
the static error pages instead of hardcoded, edX-specific values.

lms/templates/static_templates/404.html

@@ -4,5 +4,5 @@
 
 <section class="outside-app">
   <h1>Page not found</h1>
-  <p>The page that you were looking for was not found. Go back to the <a href="/">homepage</a> or let us know about any pages that may have been moved at <a href="mailto:technical@edx.org">technical@edx.org</a>.</p>
+  <p>The page that you were looking for was not found. Go back to the <a href="/">homepage</a> or let us know about any pages that may have been moved at <a href="mailto:${settings.TECH_SUPPORT_EMAIL}">${settings.TECH_SUPPORT_EMAIL}</a>.</p>
 </section>

lms/templates/static_templates/server-down.html

 <%inherit file="../main.html" />
 
 <section class="outside-app">
-  <h1>Currently the <em>edX</em> servers are down</h1>
-  <p>Our staff is currently working to get the site back up as soon as possible. Please email us at <a href="mailto:technical@edx.org">technical@edx.org</a> to report any problems or downtime.</p>
+  <h1>Currently the <em>${settings.PLATFORM_NAME}</em> servers are down</h1>
+  <p>Our staff is currently working to get the site back up as soon as possible. Please email us at <a href="mailto:${settings.TECH_SUPPORT_EMAIL}">${settings.TECH_SUPPORT_EMAIL}</a> to report any problems or downtime.</p>
 </section>

lms/templates/static_templates/server-error.html

 <%inherit file="../main.html" />
 
 <section class="outside-app">
-  <h1>There has been a 500 error on the <em>edX</em> servers</h1>
-  <p>Please wait a few seconds and then reload the page. If the problem persists, please email us at <a href="mailto:technical@edx.org">technical@edx.org</a>.</p>
+  <h1>There has been a 500 error on the <em>${settings.PLATFORM_NAME}</em> servers</h1>
+  <p>Please wait a few seconds and then reload the page. If the problem persists, please email us at <a href="mailto:${settings.TECH_SUPPORT_EMAIL}">${settings.TECH_SUPPORT_EMAIL}</a>.</p>
 </section>

lms/templates/static_templates/server-overloaded.html

 <%inherit file="../main.html" />
 
 <section class="outside-app">
-  <h1>Currently the <em>edX</em> servers are overloaded</h1>
-  <p>Our staff is currently working to get the site back up as soon as possible. Please email us at <a href="mailto:technical@edx.org">technical@edx.org</a> to report any problems or downtime.</p>
+  <h1>Currently the <em>${settings.PLATFORM_NAME}</em> servers are overloaded</h1>
+  <p>Our staff is currently working to get the site back up as soon as possible. Please email us at <a href="mailto:${settings.TECH_SUPPORT_EMAIL}">${settings.TECH_SUPPORT_EMAIL}</a> to report any problems or downtime.</p>
 </section>