New PHP API for favorite questions

Currently the API stores a title, a description, and a username in
the database, which will be used to allow the user to populate a
new question with whatever values he stored as a "favorite" earlier.
Do not link favorites to users; make them global

After a design discussion, we decided that favorites should not be
linked to users, but should be global; anyone with the right to
create questions should have access to the list of favorites.
In-progress: rename favorite to question template

This is commit 1 of 2; this one renames files, the next commit will
modify files to rename classes and functions.
In-progress: rename favorite to question template

This is commit 2 of 2, renaming classes and functions.
Allow creating questions from templates

The "Make Question into Template" and "Save as Template" buttons
aren't implemented yet, so users can't actually create new templates.
But if there are templates in the database (such as the ones I added
by hand to test this functionality), they can now be selected for new
questions. The next commit will allow saving new templates, at which
point the templates feature will be fully implemented.
Implement template creation

Now question templates work in both directions: turning a question
into a template, and creating a new question based on a template.
Notify user when template operations succeed
Add "remove templates" feature to site admin
Allow editing templates from site admin page
Merge branch 'feature/favorites'

Conflicts:
	src/angular-app/sfadmin/js/controllers.js
	src/service/sf.php