LDAP: set filter mode to raw, so filters will not be changed and broken after upgrade from oc5, when visiting the LDAP settings and opening filter tabs
get the correct version number for compare -.-
bump version and don't overwrite values on next update if not necessary
simpler and better readable assignment
Merge pull request #8579 from owncloud/ldap_nail_filter_on_upgrade

LDAP: fix filter can be reset and broken after upgrade from OC 5