Fixing small QBluetoothServer issues

-extending documentation
-emit error signal when setting a new error

Task-number: QTBUG-32669
Change-Id: I16b8a149792ed5068a7bd76af874477084802aea
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Emit ServiceLookup signal in QBluetoothSocket/Bluez when required.

Change-Id: Ide9d2cf7fd469e28c584c557ad9e1307aec37f1d
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Fix peer to peer communication using two local adapters.

The code assumed to use the default adapter in a variety of places
which caused wrong SDP registrations, device searches and peer names.

The btchat examples was extended to cope with two local adapters. If there are
more than two local adapters they will be ignored.

Change-Id: I27d8bce65d943773e4e6cbd86982446fa79664a4
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>