Use fixed templates for glance configuration

This change moves away from the template generation to using fixed
template files.  This allows us to conditionally write blocks of
configurations, which I have done for the swift_store options.

This work is largely ripped from @cloudnull's cdc branch.  Note that
there are a few minor configuration changes introduced here by
(from @cloudnull's branch), such as worker count in glance-api.conf.
Glance configuration changes

This change makes notification_driver configurable and only writes
messaging configuration options to glance-api.conf if
notification_driver is set to 'messaging' (it defaults to 'noop').

We also set a default value for 'swift_store_endpoint_type' so that
an ansible run will not bomb if the user does not have
'glance_swift_store_endpoint_type' defined in their user_variables.yml
file.
Merge pull request #96 from mattt416/change_glance_config_generation

Glance configuration changes