Add pylint tox environment and disable all existing warnings

Add pylint tox environment and disable all existing warnings

pylintrc update disables all warnings that currently trigger on neutron
code.  The rough plan is to slowly re-enable warning categories as we
clean up code in question.

This change also includes a few ultra-trivial syntax cleanups where it
allowed the check to be immediately enabled for the rest of the
codebase:

- Added missing trailing newlines in several files
  (db/migration/__init__.py, nuage/{nuagedb,syncmanager,common/config}.py)
- Renamed self to cls in @classmethods
  (cisco/db/l3/device_handling_db.py)
- Removed whitespace around '=' in a kwarg
  (cisco/db/l3/device_handling_db.py, cisco/db/n1kv_db_v2.py)
- Updated deprecated pylint 'disable-msg' directive to newer 'disable'
  (cisco/extensions/qos.py)
- File-specific disable for too-many-format-args pending further
  investigation of alternatives
  (ml2/drivers/arista/arista_l3_driver.py)
- Import module rather than object and avoid long line
  (services/l3_router/l3_arista.py)

Change-Id: Ifb0a1a38e33f9073a78658ca578fbd2a42747724