improve signatures for copy constructor and assignment operator for GattServer
GattServer:: improve default constructor
move descriptorCount into nRFGattServer
minor cosmetic change.
nrfGattServer:: move constants into the class.
nRFGattServer:: simplify header includes
extending ConnectionCallbackParameters_t
Release 0.2.3
=============

Features
~~~~~~~~

* Add nRF51GattServer::initializeGATTDatabase() to have an explicit commit
  point where the underlying GATT server is populated.

* Extend ConnectionCallbackParameters_t to include peer_addr.

Bugfixes
~~~~~~~~

none

Compatibility
~~~~~~~~~~~~~

Works with 0.2.4 of BLE_API.