Refactor page moving.

Rather than taking place immediately, and potentially breaking due to
excessive time required within a request/response cycle, page move is
now a Celery task. The user who requested the move will be notified
via email once the move is complete.

Page moves also now run in a transaction and only commit if
successful, and have more robust error catching and reporting. Errors
are logged, as well as being sent to the user who requested the move,
and in the case of unknown/unexpected errors, include the traceback
for diagnosis.
fix bug 915092 - Complete docs main page redirect
fix bug 922855 - Show banner to all redesign people
Ensure search term is in user's desired case
Merge pull request #1444 from ubernostrum/page-move-background

Refactor page moving.
Merge pull request #1456 from darkwing/redesign-banner-922855

fix bug 922855 - Show banner to all redesign people
Merge pull request #1455 from darkwing/redirect-docs-main-915092

fix bug 915092 - Complete docs main page redirect
Merge pull request #1457 from darkwing/search-uppercase-bad

Ensure search term is in user's desired case
Fix bug 922880 - Typo in register template
Merge pull request #1459 from Elchi3/typo-922880

Fix bug 922880 - Typo in register template