Move functionality into backend, rearrange data in output

Rearrange data: the outputs of get_all_devices() and get_device_data() are combined into self.gw_devices. Binary_sensors, sensors and switches are included with all their attributes, in lists.
Two classes have been added (entities.py), one for master_thermostats and one for binary_sensors, these classes now handle the processing of data previously done in plugwise-beta (climate.py and binary_sensor.py).