Code generation speed up for cbmc

[Skypr]

In the for loop "for_all_voters", place assumes inside, because less variables and clauses are created by cbmc in that case, which should speed it up a bit for bigger numbers for voters / candidates

[bigolol]

I just fixed a bug in code generation so please wait a couple minutes

This would be very difficult to implement.
Right now the CodeGeneration works totally different.
Because of performance beeing not one of the greatest goals of our program this enhancement doesn't have to be implemented.