Improve the PathSimulator

[hillmich]

The PathSimulator has some issues which are no deal breakers, but should be fixed before continueing to work on it.

• The handling of the gate costs may lead to performance degradation.
• Generating the lookup table for the gate costs should be part of library and the input format should be documented.
• The tests do not actually test as much as they should.

More details on the parts to work on can be found in #105