+ Fix the way the local package is being loaded through the resource system.
+ Allow the user to configure the name of the branch that can be used for releases.
Merge remote-tracking branch 'mark/release_vcs_branch_check' into testing_1

Conflicts:
	src/rez/release_vcs.py

added support for plugin-type-wide settings, and moved 'releasable_branches'
there, since this would be applicable to many VCS impl's.