Vast hack to make Model objects Safe for Fluid Vecs

Still in progress, does not compile, touches far to much code - because
the old Model object was not encapsulated enough.
Cleaner, Simpler API for model representation & scoring.
Frames carry a notion of a chosen response column.
Still need to yank "toJSON", move VA into interested submodels (GLM,
existing RF)
Scoring on the new models still missing critical pieces
Partial update, still not compiling
Pull back in old model as OldModel

For GLM, KMeans & PCA use OldModel with VA's.
New Model is for fvecs.
Compiles, fails instantly on tests
DRF, GBM moved to new model class

Model requires response-var in the frame, but the model-builder does NOT
want the response in the frame.
Get scoring further along

Now in the DRF score logic needing implementation
Missed some changes
merge with master
Compile error, OldModel in new code