Add manila specific hacking checks

Add manila specific hacking checks (copied over from nova) to test:
- [M319] Validate that debug level logs are not translated.
- [M323] Ensure that the _() function is explicitly imported to ensure
  proper translations.
- [M325] str() cannot be used on an exception.  Remove use or use
  six.text_type()
- [M326] Translated messages cannot be concatenated.  String should be
  included in translated message.

Also include some tests for the above (copied from nova and adjusted).

Rework HACKING.rst to remove the content that is in the global hacking
file and add in the manila specific rules.

Change-Id: I530609a183c81ba942623b73d5f62cd338b04211
Merge "Add manila specific hacking checks"