add the missing public_r method.
adjust ssh_access_controller for useful errors

The controller should now always return a valid response,
in the sense of communicating with the command-line script.
If an error occurs the json contains the error-information.
add spec to test out the ssh-access controller.
Merge branch 'fix_hets_version_checking' into 702-fix_git_clone
Merge pull request #703 from ontohub/702-fix_git_clone

Repair git clone, fixes #702.