Address the 'ART' Issue

Rather than outright remove this completely, address primary concerns:

* Add a more verbose warning message on alert dialog
* Explicitly state experimental form
* Explicitly state not supported (no bug reports)
* Explicitly state issues (crashes, bootloop, etc)

Additionally, move option to 'Apps' header (bottom), as this is it's
primary impact.

Change-Id: Icf103b5576c8e93f8a30ccd348476bf207401355
[2/2] Settings: Pimp up ActiveDisplay
Base part: https://gerrit.omnirom.org/#/c/2819/

Change-Id: I8abf7a3018e7e0168860861ac240975cd1f8a2b0
[2/2] Settings: Fix pimp up ActiveDisplay
Base part: https://gerrit.omnirom.org/#/c/3380/

Change-Id: Ief2aa6802ad25a86b49d06bab1b9e34140dc5db5