Update contrib docstrings to match guidelines

Per http://docs.openstack.org/developer/hacking/
and http://www.python.org/dev/peps/pep-0257/

Without extra blank line in multi-line docstrings
based on http://lists.openstack.org/pipermail/openstack-dev/2014-February/028156.html

Blueprint: reduce-flake8-ignored-rules

Change-Id: I0050d382369d3013280f3d90df87fb530bc6c939
Cherry pick oslo-incubator db fixes

The patch cherrypicks 2 fixes related to utf8 migration:

 * Ib5c0f93c788afda92aad862e50dc086dc39605f1: Ignore migrate versioning tables in utf8 sanity check

 * I7f271d846141ac72dde3fb0d12159b125018eb2c: Make table utf-8 charset checking be optional for DB migration

Change-Id: Icb811e846c05f863a42611054f2e3f30a47573db
Closes-Bug: #1301036
Merge "Cherry pick oslo-incubator db fixes"
Merge "Update contrib docstrings to match guidelines"