Android: Add ability to (dis)connect to BTLE devices on Android

and keep tracking the connection state

Change-Id: If4d05fa18c78802ae06096884fba78eed123e77f
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Add enum for failure to connect to remote BTLE device.

In addition we restrict the emission of disconnected()
signal on Android to those cases when we had an established
connection.

[ChangeLog][QtBluetooth][QLowEnergyController] QLowEnergyController::ConnectionError
enum value added.

Change-Id: I3602e303e61a872855925a26e695f2bc880cf540
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Make compile unit tests

The ControllerState and Error enums were recently registered declared
via Q_DECLARE_METATYPE. This fix removes the duplication and resulting
compile error.

Change-Id: I38233bc067f7d94fd0dbfefbf5a6a2b08d2c6a49
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>