Extracts CBCentralManagerDelegate implementation.

All the logic regarding CBCentralManagerDelegate is extracted
into a class.

Public interfaces for device discovering and connection has
been extracted to protocols and the only way to get a
concrete implementation of this protocols is through
WLXBluetoothDeviceManager.
Exatracts connection record persistance.

Storing the last connected periphheral to the repository
is now responsability of WLXBluetoothDeviceRegistry.