Tweak is_admin() such that `user == OS username` is implicitly assumed to be an admin.
Remove erroneous svn.ci().
Implement TestRepo.component_depth(_full) properties.

Helper properties for getting the repo component depth (via
evn:component_depth).
Implement @ensure_component_depth decorator and update tests accordingly.
Add set-repo-component-depth and get-repo-component-depth commands.
Add missing component-depth tests to TestSingleToMultiRepoConversionSimple.