Added support for notes with several levels with the following meaning:

• level=0 is a warning;
• level=1 is an important action (used in witnesses comparison by default);
• level=2 is a helpful hint for witness visualization;
• level=3 and above are other type of notes (currently are not used).

Multiple Error Analysis (MEA) stands for automatic violation witnesses filtering.
Usage:

./scripts/mea.py -d <directory with violation witnesses>

All unique violation witnesses will be printed as a result.