RepositoryInfo had two old flags for indicating support for features,

supports_changesets and supports_parent_diffs. Having these in

the RepositoryInfo class was weird, since we have a bunch of other

support flags that live on the SCMClient class. Whether a client

supports these isn't something that might change from repository to

repository, so these should live on the client too.
This change moves those flags over. Unfortunately, unlike a lot of the

recent cleanups, this isn't something that can be done in a soft

deprecation. It seems pretty unlikely that there are custom SCMClient

implementations floating around which use these, but just in case, if

they try to use it after upgrading to RBTools 3.0, it'll spit out a

useful error message telling them how to fix it.

Ran unit tests.