Refactor / fix several bugs in the Bluetooth threads, closes #197

[jverbraeken]

• Relevant Issues: #197

• Related Pull Requests: #195

• • *

What

This Pull Request adds to the repository

• A boolean to the cancel method of AndroidBluetoothConnectThread that decides if the socket should be closed
• Makes EspressoTestMatchers in QRExchangeKeyActivitySteps static final, because findbugs complained
• A new exception, thrown when a socket could not be created
• Delegations to the Bluetooth threads so that the thread creator can exert better control over the thread's behavior and to better localize all concurrency related operations
• Thread synchronization on a lock instead of the object itself
• A better exception naming format by allowing exception names like e2

Why

This Pull Request is needed because the socket of connectthread is never closed when the user is never connected, but only initiates the request.

How

This feature can be viewed/tested within the project by verifying that Bluetooth still works.

Alternative implementation

Other implementations that I've have considered are

Notes

#195 should be merged first

[clenrock]

Closed because it didn't work and we were unable to debug the cause