Video generators has been extracted into strategies classes

Video generators have been extracted into strategies classes, in order to get rid of IF acrobatics in conred.self.new and not to change that code after a new strategy is added.

Meaning that adding a new strategy is pretty straight forward now  - 1)add a new strategy 2)Insert the strategy into available strategies array (can get rid of the array and use config file later on).

There are no specs provided, since only internal behaviour has been changed, which is already covered.