#198 Add alternative second approach to apply state requirement invariants during data-based synthesis

• Best to review per commit, I think.
• We now have two approaches to apply state requirement invariants for data-based synthesis.
• Added an option to choose between the two approaches.
• Changes are essentially backwards compatible, but do lead to some changes in debug output.
• The option has no effect on the benchmark models, as the don't have any state requirement invariants.
• I tried to document the new option in a way that explains its effects. But, it is quite advanced. It may not be super easy to read for many users.
• Some small code improvements, including splitting some methods.
• Some small documentation improvement.

Closes #198 (closed)