* Change of behaviour. Allow user to configure either a position topic or a state topic but not
both.
* optimistic mode in set_cover and tests added
* optimistic mode in set_cover_position using percentage_position
* fixes accroding to Martin review.
* added validation schema for set_position_topic and get_position_topic
* check only set_position_topic in supported_features.
* Multidoc string fix.