Enable LAN plugin when providing a wifi access point

Closes #1171

See merge request akwizgran/briar!752

Shut down cleanly when phone is shutting down or memory is low

Closes #1190

See merge request akwizgran/briar!742

Looks like I added the last commit after the MR was merged.

Shorten and clean up various strings, remove empty forum warning bubble

See merge request akwizgran/briar!741

Hide UI during shutdown

See merge request akwizgran/briar!737

Add denormalised columns to messageDependencies table

See merge request akwizgran/briar!733

Add fullscreen button to QR code view

Closes #346

See merge request akwizgran/briar!734

Show different notification settings for Android O

Closes #1159

See merge request akwizgran/briar!727

Use WifiManager to get wifi network information

Closes #845

See merge request akwizgran/briar!743

Discard tasks submitted to ScheduledExecutorService during shutdown

Closes #1184

See merge request akwizgran/briar!739

This ensures we bind to the wifi interface even if it doesn't have internet access and there's another interface with internet access (e.g. mobile data).

Remove mention of pen icon from forum empty state message

Closes #965

See merge request akwizgran/briar!740

Show viewfinder again after connection fails

Closes #1177

See merge request akwizgran/briar!735