XWIKI-9738: Finalize migration from workspaces to the new wiki API.

* Add new migrators to xwiki-enterprise-data.
XWIKI-9738: Finalize migration from workspaces to the new wiki API.

* xwiki-enterprise-migrator is not necessary anymore.
Merge pull request #57 from gdelhumeau/XWIKI-9738

XWIKI-9738: Finalize migration from workspaces to the new wiki API.