Move access tabs into a vertical tab set up within a "permissions" tab

This was discussed first in #11634 but at that time it was not a step forward due to issues with vertical tabs and toolbars making it huge. Rebased to latest master it looks a lot better thanks to a bunch of @exside's fixes!

Before:
![before](https://cloud.githubusercontent.com/assets/312944/3652079/5fccf540-1133-11e4-8d6c-26efd3c4a258.png)

After:
![cursor_and_user_group__administrator___modx_revolution](https://cloud.githubusercontent.com/assets/312944/3652072/41f26e4c-1133-11e4-832c-c82697ec13aa.png)