Clean up reviews/urls.py.
Clean up reviews/urls.py.

This cleans up reviews/urls.py by separating out rules with common
prefixes into urlpatterns that can be included.

There are still some prefixes that remain across rules within a
urlpatterns block (the review e-mail previews), but those seemed to make
more sense kept together.

sgallagher/reviewboard,beol/reviewboard,reviewboard/reviewboard,1tush/reviewboard,brennie/reviewboard,1tush/reviewboard,brennie/reviewboard,KnowNo/reviewboard,1tush/reviewboard,bkochendorfer/reviewboard,KnowNo/reviewboard,custode/reviewboard,reviewboard/reviewboard,beol/reviewboard,davidt/reviewboard,davidt/reviewboard,custode/reviewboard,1tush/reviewboard,1tush/reviewboard,sgallagher/reviewboard,1tush/reviewboard,chipx86/reviewboard,brennie/reviewboard,bkochendorfer/reviewboard,reviewboard/reviewboard,davidt/reviewboard,bkochendorfer/reviewboard,1tush/reviewboard,chipx86/reviewboard,beol/reviewboard,1tush/reviewboard,custode/reviewboard,1tush/reviewboard,bkochendorfer/reviewboard,custode/reviewboard,beol/reviewboard,KnowNo/reviewboard,chipx86/reviewboard,sgallagher/reviewboard,reviewboard/reviewboard,chipx86/reviewboard,davidt/reviewboard,sgallagher/reviewboard,brennie/reviewboard,KnowNo/reviewboard