Compile a subset of Scala to SPIR-V

[szymon-rd]

DSL and GIO may be good enough, but in a perfect world we compile parts of our program into SPIR-V. Those parts would be the lambdas in GFunctions and all other code they use.

I am not sure if that is feasible, macro annotations will definitely help. Some features will need to be left out and throw errors.

[MarconZet]

I think caching shader compilation solves this problem. Alternatively we could provide an alternative run target that just collects all GPrograms, compiles them and exits. Then we could check resources for precompiled programs.