bhutils as helper-tool

[safl]

We have the helper-tool bhutils.py, however, it does not install as a command. It would be useful to make it available as a command and while doing so adding a couple of features:

• Update it to also parse "stacks" in addition to "children-chaining"
• Make it runnable as bhutils
• Enable test-runs such as: bhutils test possibly with multiple granularity bhutils test python, bhutils test cpp or something like that and while looking at testing, document how the various testing systems work.