Refactor OSX hashdump post module.

* Adds support for MATCHUSER regex option
* Adds support for OSX 10.8 and 10.9 hashes (PBKDF2)
* DRYs up a bunch of older code, adds lots of helper fns
* Ends up shaving off ~20 lines
Fix description, kill dead constant.
Fix MATCHUSER bug.

* Also add spacing and indentation for better readability.
* Refactors grab_shadow_blob method.
Supports 10.3
Make pipe part of /bin/bash cmd.
Make sure loot is named correctly.
Add user param to nt_hash call.
Revert read_file to cat so that pipe will work.
Land #2735, @jvennix-r7 support of 10.8+ on osx hashdump