Use extended SDP discovery in btchat example.

Android's minimal service discovery is very limited and more often than
not fails entirely. Using FulklDiscovery dramatically increases the
chance to find the remote SPP chat server.

Task-number: QTBUG-38140
Change-Id: I1df55f74a6896312236ef06485c4063c9e893e6c
Reviewed-by: Nedim Hadzic <nhadzic@blackberry.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Build snippets during developer builds with examples only.

This replaces an earlier Android specific solution against
a more generic solution.

Task-number: QTBUG-37638
Change-Id: I472ea48567e872c658094a5576b9260bf2d02c89
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Fix inconsistent behavior between BtDiscoveryModel & BtServiceDiscoveryAgent

The model always resets the model content when starting a new service
discovery. However QBluetoothServiceDiscovery doesn't do that. It adds
newly discovered services and maintains the existing services. Since
the model updates its content based on the serviceDiscovered signal,
every second run created an empty list or only ever added services.

Change-Id: I9c1d29562b9178678ab42bee98d5d1e3d0c4367f
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>