Add lib module for using mailbox as a library, especially in briar integration tests

See merge request !115

Add parameter that can be used to instruct mailbox not to exit on stop

Closes #158

See merge request !121

Fix DoNotKillMeFragment from getting re-created preventing users from proceeding

See merge request !122

Otherwise, it gets recreated with the view model.

 The system state is updates async on Xiaomi devices, so we need to give it a bit of extra time before showing a dialog.

preventing users from proceeding

Let StatusManager combine all sources into single app state

Closes #122, #155, and #159

See merge request !119

This fixes a number of subtle issues that happen for example on screen
rotation or when the activity gets destroyed and recreated.

Make onboarding readable on small landscape screens

Closes #152

See merge request !120

Get rid of OnboardingActivity, use a fragment in MainActivity instead

Closes #144, #150, and #153

See merge request !117

After pairing completed, show success screen

Closes #151

See merge request !114

Move fragment navigation to activity

Closes #144 and #141

See merge request !112

Fix navigation bug when finishing onboarding

Closes #142

See merge request !110

The bug occurs when finishing onboarding while having the
do-not-keep-activities developer option enabled.

Return 404 for missing or unauthorised folders

See merge request !111

Fix power view icons being cut off; add text margin

Closes #146

See merge request !109

Backport recent changes from Briar TorPlugin

See merge request !103

Don't crash when navigating to do-not-kill-fragment after dozing

Closes #145

See merge request !108

This activates automatic bridge usage