In some cases when there are no longer any files this caused error since filediff wasn't present.
In addition this generated wrong ids since it used a last-defined attribute on a for loop.
Fixes#5567
- This change will allow SVN to execute rhodecode integration framework
via executing the builting hooks.
- uses txn_id for svn to provide metadata required via Apache
- Interception of SVN transaction is required to use temporary stores for metadata
- hooks are now part of vcsserver where the install/control logic is stored
