Added the migration for adding the resourcebase_ptr_id field in layer.
Merge branch 'migrations' of https://github.com/capooti/geonode into migrations

Conflicts:
	geonode/layers/migrations/0006_fetch_initial_geoserver_data.py
	geonode/layers/migrations/0012_fetch_initial_geoserver_data.py
	geonode/layers/migrations/disabled/0010_fetch_initial_geoserver_data.py