Add missing InvalidBluetoothAdapterError to QML discovery model

QBluetoothServiceDiscoveryAgent::InvalidBluetoothAdapter was introduced
by Qt 5.3 but never added to the QML BluetoothDiscoveryModel. This patch
fixes the problem.

This was noticed due to a crash on Android emulator.

Change-Id: I652576929659ca370216133154e36158e8425711
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>
Fix crash during service discovery on Android

This is caused when running a service discovery on an Android emulator.
The emulator does not have a local Bluetooth device despite the Qt code
assuming it.

Change-Id: I9c0d826d14e7494bfeb27d449f9b6f568860d917
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>
Merge remote-tracking branch 'origin/5.4.0' into 5.4

Change-Id: I3f85a68066352e0b163f47d2b8ada1d0b8d34f33
Improve documentation for undiscovered QLEService

The class' behavior strongly deponds on its state. This can be
confusing. This patch reduces the behavior uncertainties.

Change-Id: Ib5cd8e821f2bb9aca5b579abf4ae98918f951f24
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>
Bump version

Change-Id: Ic018bf8b03e887da5448e0bcd6fdb18219fad184
Merge remote-tracking branch 'origin/5.4' into dev

Conflicts:
	.qmake.conf
	src/bluetooth/qlowenergyservice.cpp

Change-Id: I4b0f68d35ea898819b7c8078b24d55ae90ee529c
Merge "Merge remote-tracking branch 'origin/5.4' into dev" into refs/staging/dev