Generator - fully-contained model

[vaind]

Instead of loading model from JSON, include all information in the generated code. Some of the information is already there, in the generated Entity_ class's static members so it may be useful to reuse that but it's not mandatory.

[vaind]

I've just noticed the model isn't using all the necessary information, such as lastEntityId - it must not be picked from the last currently present entity but rather explicitly stated, because it doesn't change even if an entity is removed. Similar applies to other last*Id variables.