use logic name for urls.
add logic-name-url support to graphs.
provide repository-clone list as text response

If the repository list is queried as text/plain it will respond with the
clone-urls for the repositories.  One can switch between the different
clone-urls via `?clone_type`, where `?clone_type=git` is the default and
`?clone_type=ssh-git` is currently the only alternative.
extract default-clone-type into constant

The default-clone-type of 'git' is now a constant in the
Repository-namespace. As this is the default clone-type the
clone_methods method will now use this as the default (instead of the
confusing `nil`).
add link to repository clone list.
Merge branch '1082-provide_url_list' into develop
Merge branch 'add_named_logic_iris' into develop

Conflicts:
	app/models/logic.rb
Merge branch 'develop' into develop.ontohub.org