The module is updated to comply with the changes to BLE API regarding correct
shutdown functionality. The following changes are introduced to ble-nrf51822:
* Calls to the old static function shutdown in Gap, GattClient, GattServer and
SecurityManager are removed.
* The cleanup function in Gap, GattClient, GattServer and SecurityManager is
renamed to `reset()` and made public.
* The static references inside nRF5xGap, nRF5xGattClient, nRF5xGattServer and
nRF5xSecurityManager to objects of their own class are moved to nRF5xn.
* The static getInstance accessors in nRF5xGap, nRF5xGattClient,
nRF5xGattServer and nRF5xSecurityManager are removed and their functionality is
moved to the implemented virtual accessors in nRF5xn i.e. getGap(),
getGattClient, etc.
* A static function Instance is added to nRF5xn class to make the transport
object accessible across the module.
