Make share_types require a driver mode

Currently the driver_manages_share_servers is an optional extra_spec on each share_type that allows the scheduler to filter. We want to make this a required extra spec, so that every share type has this value set to true or false.

The share-type-create command should have an additional required argument which specifies whether the extra spec is true or false after share type creation.
It should not be possible to remove that extra spec.
Modifying the extra spec is allowed as long as the value remains either true or false.

The share-type-list API should be modified to report the value of the driver_manages_share_servers=True/False extra spec for each share_type.
The API should also include a flag indicating which share_type is the default.

Manila should refuse to start if no default_share_type is specified. If the default share type is defined but does not exist, share creation with not share type should fail. Devstack should automatically create a share type and set the name to match the default in the config file.