* define storage item for holding historical DKG state
* make all epoch storage operations go through proxy functions
* make each saving action also apply to the historical item
* removed usage of update_epoch function
* test correct save heights
* exposed query for the epoch state at specified height
* regenerated contract schema
* restored default cw-plus behaviour as in hindsight it makes more sense
Jędrzej Stuczyński
e9165763b6