[1/2] Settings: Add Captive Detection toggle

http://jira.omnirom.org/browse/OMNI-356

Change-Id: I284ce5951c9c4bf8a6875e129a947fb3912df71d

Patchset: 6
https://gerrit.omnirom.org/#/c/4827/
Settings: Don't crash if we pause too quickly

Notifier is unregistered in every case in pause.
However, if you close the Settings app too quick, the notifier
might not be registered at all, causing an IllegalArgumentException
during the unregistering.

Change-Id: I54141cbfc91d08c28ef524f4155b673ae8dee90e
Build V42.3-private