BQP with QR codes

This MR implements BQP for key agreement over short-range transports. It also implements the Android UI for using BQP with QR codes.

Closes #117.

See merge request !84

The signature covers the forum post body, not the message body.

Save queue state before delivering message. #272

Another attempt to fix #272...

See merge request !125

Transaction isolation. #272

When client transactions were implemented the DB's read-write lock was removed, exposing H2's transaction isolation semantics. The default isolation level is "read committed", which allows concurrent transactions to overwrite each other's updates. This was the cause of #272. Changing H2's isolation level to "serialisable" would have caused other problems.

The solution is to reintroduce the DB's read-write lock. The lock is acquired when starting a transaction and released when committing or rolling back a transaction. (We already use try/finally blocks to ensure every transaction is committed or rolled back.) Read-only transactions can share the lock. To avoid deadlock, transactions must not be started while holding other locks.

This patch adapts the key manager to the new locking rules. The rest of the code was already compliant. Transports are now added to the DB during the startup phase, which allows TransportAddedEvent and TransportRemovedEvent to be deleted.

Fixes #269, fixes #272.

See merge request !124

TransportPropertyValidatorTest

Tests for the TransportPropertyValidator ValidateMessage call.

See merge request !110

Fixes #270.

@color/briar_text_primary is used in a lot of places other than the settings screen - if we want to use grey text in the settings screen we'll need to find another way.

Also fixed some misspelled resource names and included the colours from the Briar palette in color.xml.

247 dagger 2

This MR in a nutshell replaces Guice and Roboguice with Dagger 2, which offers a lot more possibilities than is implemented in this branch, such as using lazy injections for performance purposes. With Dagger 2 all the magic happens at compile time, so no need to worry about unfulfilled injections at runtime, but due to restrictions I was forced to put injected test code into an Android module. We therefore have a new test module, `android-test`.

A consequence of using Dagger 2 is that we no longer have a view injector and I therefore had to replace those with manual references. 

Closes #247 

See merge request !118

Modified the project structure, removed module extension and went instead for a non-complete core dependency graph

Semi-encapsulated the core/api dependency graphs and created a proper structure to load eager singletons