The Model was getting unmaintanable mess. This is an attempt to refactor/rewrite the Model so that data of certain type is exposed in standardized way, offering certain standard manipulations for that data type, and on the GUI side, certain standard widgets to tied to that data.
This rewrite closes#72, #106 and #120.
The RPC and sync library mechanisms were removed for now; they never really worked and contained several obvious bugs. Need to consider if syncs are useful at all during the compose time, or just used during intro.
