Upgrade our branch-api version and misc changes

This CL contains several changes:
1) Finally remove the "properties: {}" stuff now that the NPE in the core has been fixed.

2) Update findbugs plugin to a newer version that emits warnings to the build log, fix a few errors that popped out.

3) Update the version of branch-api we depend on to include my recent PR that removes the requirement that branch name == project name.  This unblocks our ability to support branches with names of the form 'foo/bar'.
elaborate on this comment?  Do you want to make the super constructor protected to be invoked by this?