Bump to 2.0.2 dev.
Merge branch 'release-2.0.x'
Change the return type of get_hosting_services.

get_hosting_services was a generator returning tuples of (id, cls) for
each HostingService. This was to work around not having a way to access
the ID from a HostingService class.

This change fixes this by assigning the ID at registration time to the
class, allowing any consumer of the class to get the ID. This simplifies
get_hosting_services(), and is also needed for the new HostingService
API resource.

Reviewed at https://reviews.reviewboard.org/r/5883/
Add an API resource for hosting services.

This introduces /api/hosting-services/, which provides basic information
on the hosting services supported by Review Board.

The resource does not expose all the information on a HostingService.
Right now, I'm keeping to the basic information, such as the name and
capabilities, until I determine what we're going to want to use for the
new repository configuration UI. This UI may impact how HostingService
itself structures data down the road, so it's not worth baking anything
related to that into the API yet.

This work is loosely based on Olessia's UCOSP work, though many
changes were made to better fit in with other resources, to take
advantage of what WebAPIResource provides, and to make use of the new
LocalDataQuerySet (which greatly reduces the amount of code).

Reviewed at https://reviews.reviewboard.org/r/5882/