Enable pylint checks for "anomalous" string escapes

Escapes in python string literals are well defined, but can be
confusing.  These pylint checks look for backslash escapes in strings
that might be mistakes.  Two code refactors were required to satisfy
these tests:

1. midonet_lib.py used \**kwargs in docstrings.

There doesn't seem to be a sphinx standard for kwargs, so this change
simply replaces them with "kwargs".

2. Regex literals containing escapes replaced with r''.

The assumption with this change (and the underlying pylint
check) is that r'' literals are more straightforward for regular
expressions, where every backslash is important.

While looking at these regexes, this change also removes a few
unnecessary "\-" escapes.

Change-Id: I01528b2482f78b9e851685ebbf6fded4e58355f1
Allow to specify IP address of floating ip

IP address of floating ip will be automatically allocated.
There are cases where users need to specify a floating IP address.
This patch addresses the problem.

The feature is limited by "create_floatingip:floating_ip_address" in
"policy.json".
By default, it needs an admin role.

DocImpact
APIImpact

Implements: blueprint allow-specific-floating-ip-address

Change-Id: Iba64a0f0a38ca5eb39c605e121a12c956637b96c
Merge "Enable pylint checks for "anomalous" string escapes"
Merge "Allow to specify IP address of floating ip"