more precompiler constants on entities

<$keyfields>, <$subtypes>, <$supertype>, <$paintedentities>

To support generated coding (we will get hardcoded lines instead of fiddeling around at runtime) on entity levels, additional informations are required. 

React flexible to modeled information of an entity.
Because this will generate hard-coded lines, the performance is much better than doing the same at runtime (bindnumber instead of "search-by-name", once rated from the lab as factor 10). 

A clearer, faster code plus the flexibility to create standard include code once to handle a range of entities.