Added the rest of the files from the old MariaDB Charm.

The following was copied with some small changes:
  - copyright

The following were copied without any changes:
  - hooks/ceph-relation-changed@
  - hooks/ceph-relation-joined@
  - hooks/cluster-relation-changed@
  - hooks/common.py
  - hooks/db-admin-relation-joined@
  - hooks/db-relation-broken
  - hooks/db-relation-joined
  - hooks/ha-relation-changed@
  - hooks/ha-relation-joined@
  - hooks/ha_relations.py
  - hooks/lib/__init__.py
  - hooks/lib/ceph_utils.py
  - hooks/lib/cluster_utils.py
  - hooks/lib/utils.py
  - hooks/local-monitors-relation-joined@
  - hooks/master-relation-broken@
  - hooks/master-relation-changed
  - hooks/master-relation-departed@
  - hooks/monitors-relation-broken
  - hooks/monitors-relation-departed
  - hooks/monitors-relation-joined
  - hooks/monitors.common.bash
  - hooks/munin-relation-changed
  - hooks/munin-relation-joined
  - hooks/shared-db-relation-changed@
  - hooks/shared-db-relation-joined@
  - hooks/shared_db_relations.py
  - hooks/slave-relation-broken
  - hooks/slave-relation-changed
  - hooks/slave-relation-departed@
  - hooks/slave-relation-joined
  - keys/repo.percona.com
  - lib/net.sh
  - scripts/
  - scripts/add_to_cluster
  - scripts/remove_from_cluster
  - monitors.yaml