Permissions UX overhaul

This set of commits changes the complex permissions UI to hopefully be a bit more sane.

![fireshot screen capture 131 - modify group - localhost_smf2_1_index_php_action admin area permissions sa modify group 0](https://f.cloud.github.com/assets/431799/2367405/d58e4eaa-a75c-11e3-859c-5395f5468e7a.png)

![fireshot screen capture 132 - modify group - localhost_smf2_1_index_php_action admin area permissions sa modify group 0](https://f.cloud.github.com/assets/431799/2367406/dbbb51a6-a75c-11e3-8238-2948e9ae6a9b.png)