[2/3] Settings: Add ActiveDisplay options via OmniGears

Base: https://gerrit.omnirom.org/#/c/2417/
OmniGears: https://gerrit.omnirom.org/#/c/2584/

Change-Id: I2376bd9037abcf34903bce43d893872ab490387d

Conflicts:
	res/xml/settings_headers.xml