bump database version to OMERO5.0__0 (beta2)
 update database schema to OMERO5.0__0 (beta2)

upgrade script from beta1 already exists
Include OMERO5.0DEV__6 to OMERO5.0__0 in upgrade from OMERO4.4__0.
Merge pull request #1842 from mtbc/db-version-beta2

upgrade database version to beta2