rosa svn-*: notify and verify users

rosa svn-pre-commit:
* verify users in owner and access-list.
* improve diagnostics.

rosa svn-post-commit:
* notify users in owner and access-list on changes.
* (format of notification email may be some further adjustment.)

User information via LDAP server or Unix passwd information.

Unfortunately, I am unable to find an easy way to mock an LDAP server, so there is no automated tests for the LDAP user tool, but tests have been performed manually using our test environment.

Improve pylint score.

Close #1113. N.B. It does not restrict owner to author on suite creation. Instead I think it is best to rely on the post-commit hook to notify the owner that someone else has created a suite on his/her behalf.
Unnecessary test?