Add an engine for running VMA in different modes. User can:
- Decide how to initialize the colors (e.g. from the Model or from
the LLVM IR)
- Decide what to do with the final TFG obtained by VMA
- Decide whether or not the Mincut algorithm should run
Candidate colors, accepted colors and content are now accessible
only with setters and getters. In this way, we can check that
the Candidates are always a subset of the Accepted colors.