Add a policy layer for membership APIs

Added a policy layer for the membership APIs of the domain
model.

Added following policies for membership APIs:

v1: 'get_members', 'delete_member' and 'modify_member'.

v2: 'add_member', 'get_member', 'modify_member',
'get_members' and 'delete_member'.

Implements blueprint membership-policy

Change-Id: I0d5782d1d9b7b8a563a689fcb192958ab3fea0f4
Use Python 3.x compatible octal literals

Python 3.x deprecated octal literals in the form
0755. Use 0o755  instead which works at least
with Python 2.6 and newer.

Change-Id: I3474f601dab0e2e1fbed8ef6f7472e3e453b94fb
Merge "Add a policy layer for membership APIs"
Merge "Use Python 3.x compatible octal literals"