Categories updates

* Consolidate all "arts" categories into "Arts & Entertainment"
* Add "Immigration" category
* Rename some categories
* Remove "Arts & Life" section from menus
* Remove "is_news" boolean from Category
* Remove "is_news" boolean from Blog

The "temporary-deployment-methods" branch needs to be merged and deployed before this one. Those temporary methods can be removed after this branch is deployed.

Todo when this is deployed:
* (nginx) Redirect all old arts categories to "/arts" (including feed)
* (nginx) Redirect "/arts-life" to "/arts"
* (nginx) Redirect /money to /business
* (nginx) Redirect "/california" to "/local" (including feed)
* Sphinx needs to be rebuilt