Load categories and locations when a new site is created

This removes the need to visit the categories or locations page
just to preload taxonomy information. That step is only necessary
for sites that have already been created.
Start tracking taxonomy schema version, only update on change

Rather than comparing locations and categories every time the edit
terms page is loaded, we should look for the current taxonomy schema
and only update when required.

The next step will be to add a cron task that performs the
comparison and update in the background.
Merge pull request #10 from washingtonstateuniversity/feature/new-sites

[PR] Pre-load taxonomy terms into new sites, start tracking schema version