Refactor PyTSEB.

[radosuav]

The main reason was to separate PyTSEB into three classes for the three existing TSEB models. This will make it easier to plug new models (e.g. ESVEP) into the PyTSEB framework.

Note: In PyTSEB and subclasses the following public function names have changed:

• run_TSEB_local_image -> process_local_image
• rub_TSEB_point_series_array -> process_point_series_array
• run_TSEB -> run