add a manager for ssh keys.
add authorized_key file hooks for SSH-Keys.
add git-user constant/config.
remove old key-management system.
add git group to config and manually chown

There seems to be an error inside of
pwd.c/h which has a function defined, that
is called by FileUtils.chown_R, which should
determine the uid based on the username, but fails
to do so (at least on Mac OS X 10.7.5).
As substitute we call chown via a system call.
Adjust git-ssh settings to current config.
remove missing actions and adjust url for git-ssh.
refactor naming of git-shell parameters.
Merge branch 'develop' into augmenting304_ssh_access_for_git

And some refactoring of the settings.

Conflicts:
	config/initializers/repositories.rb
Merge branch 'develop' into augmenting304_ssh_access_for_git
One step more towards SSH access
KeysControllerTest translated into RSpec.
Merge branch 'augmenting304_ssh_access_for_git' into develop
Merge branch 'develop' into develop.ontohub.org

Conflicts:
	config/settings/production.yml