Add momentum and angular momentum physical types. I'm not sure, but it seemed like an omission to me--for example the physical type of hbar was 'unknown'
Add more units and physical types
Simplify some of the physical type descriptions as per feedback by @astrofrog in PR.
Fix test bug now that u.Bq is the same as u.Hz
Merge pull request #1072 from mdboom/unit/more-physical-types

Add more units and physical types