Added per user-tenant quota support

Added per user-tenant quota support.
Added user-quotas extension, that turns on user quota support if it is
loaded.
Added force parameter, that lets to ignore check if admin want to
force update when run 'manila quota-update'
Added 'extended-quotas' extension that has provides ability for admins
to be able to delete a non-default quota (absolute limit) for a
tenant, so that tenant's quota will revert back to the configured default,
and makes the force parameter always be passed if the client wants
to set the new quota lower than what is already used and reserved.
Added user quota support to db.api, sqlalchemy.api, sqlalchemy.models.
Added migrations for user quota support.

Implement bp: user-quota-support

Change-Id: Ifb8f8a041c2fa54e2ed3a8219e87607b161438ca
Merge "Added per user-tenant quota support"