#171 Allow optimizations to be choosen on per-class basis

[Asking_questions]

Some of optimizations are hardly usable without this ability. For example, most wise people won't ever enable class merging at all, because benefits from method inlining etc. in entire program far outweigh ability to merge few classes, supporting that. This would come especially handy for generated code - which is guaranteed to follow certain constraints and as such can be optimized much more aggressively.