Make code generator more modular

[cvogt]

Currently the code generator is one large class (hierarchy). This is great for getting started and advancing but for more advanced use the class can be an obstacle and individual functionality would be nice to be accessible without using the class at all. We should refactor things like name collision avoidance and default value generation out of the generator to be usable independently.

[aaggarwal35]

+1
It was hard to figure different options to override in the correct format. (fyi, using slick 3.0)

[cvogt]

we could export a few common use cases in a simpler format but for more advanced stuff you'd have to use the overrides