Refactoring migrations.
Added the migration for adding the resourcebase_ptr_id field in layer.
Added the migrations to move layer stuff to base.
Some more steps added.
Intermediate commit for Simone.
Now resource_base is correctly populated with layers.
Now importing spatial representations, restriction codes, topic categories and regions from layers to resourcebase.
Merge branch 'master' of github.com:GeoNode/geonode into migrations
First working version for 1.2 to 2.0 migrations.
Now the permissions, styles and other notable stuff is migrated.
Last commit before doint the migration PR.
Added documentation for migrating from 1.2 to 2.0.
Merge pull request #1326 from capooti/migrations

Added the migrations for migrating a GN 1.2 instance to GN 2.0