A common requirement for multibranch plugins is to create specialized sub-views that are filtered by the different types of branch. Given that some plugins have half-complete hacky implementations of this, we should provide a correct base implementation so that plugins can have a simpler path to doing the correct thing.

(note; half complete because it assumes that it only ever will be applied to a WorkflowJob rather than correctly navigating to the BranchProjectFactory and then using that to access the Branch instance... thus the utility of that class is compromised relative to what it should be)