This icommit adds several changes related to the same topic
- resetting a Runner registration token:

1. On Project settings page it adds a button for resetting the
   registration token and it removes the Runner token field
   that was confusing all GitLab users.

2. On Group settings page it adds the same button for resetting
   the registration token.

3. On Admin Runners settings page it moves the button to the same
   place as in Project and Group settings and it changes slightly
   the page layout to make it more similar to Group and Project
   setting pages.

4. It refactorizes a little the partial that prints runner
   registration description. Thanks to this Project, Group
   and Admin settings of the Runner are re-using the same
   code to generate the button.

5. Updates the translations of changed text.