add drop-type support for rake db:migrate:clean

This is needed since we now create Types
in some migrations.
Updated rails to 3.2.17.
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.
change hets date checking to revision checking.
document the extended postgresql-types method.
Merge pull request #696 from ontohub/fix_rake_db_migrate_clean

add drop-type support for rake db:migrate:clean
Merge branch 'fix_hets_version_checking' into 702-fix_git_clone
Merge pull request #704 from ontohub/fix_hets_version_checking

Change hets date checking to revision checking.
Merge pull request #703 from ontohub/702-fix_git_clone

Repair git clone, fixes #702.
Merge branch 'staging' into develop