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

Show different notifications for each state

Closes #123 and #140

See merge request !105

in order to update foreground notification

Upgrade KTor to 2.0

Closes #143

See merge request !107

Resolve "Clear UI when mailbox is wiped remotely"

Closes #114 and #113

See merge request !99

Fix layouts, improve UI in landscape mode and small screens

Closes #130 and #131

See merge request !104