Move GlobalBundleScanningSchemaServiceImpl to its own bundle

Move GlobalBundleScanningSchemaServiceImpl to its own bundle

Moved the GlobalBundleScanningSchemaServiceImpl and the associated
BundleActivator, SchemaServiceActivator, from sal-dom-broker to a new
bundle sal-schema-service.

A couple reasons for this. One is to break the circular service imports
between sal-dom-broker and sal-distributed-datastore, where
sal-distributed-datastore imports the SchemaService from sal-dom-broker
and sal-dom-broker imports the DOMDataBroker from
sal-distributed-datastore. The result of this was that if the
sal-dom-broker blueprint container was restarted, it would also cause
the sal-distributed-datastore container to restart, which isn't
necessary/desirable.

The other reason is that apps can register a SchemaContextListener as an
OSGi service which is picked up by the
GlobalBundleScanningSchemaServiceImpl. In terms of service usage this
makes sal-dom-broker a dependency of the app bundle so if the app
container restarts, it also restarts sal-dom-broker,
sal-distributed-datastore etc which isn't desirable.

So moving the GlobalBundleScanningSchemaServiceImpl to its own bundle
alleviates both issues.

Change-Id: I75d1009f6bfc1d80a19a61050703a1ca7e049575
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>