#196 Add DCSH variable ordering heuristic.

• Added choice/reverse wrapper variable ordering algorithms.
• Added DCSH variable ordering heuristic.
  • Is for now based on graphs constructed from the original hyper-edges.
    • Could later create DMSs/hyper-edges based on the paper's approach.
  • Is for now based on total span.
    • Will later also adopt the WES metric (a next merge request).
    • Until we introduce the WES metric, the reverse orders are never chosen, as reversing the order has no effect on the total span.
• Added option to data-based synthesis tool to enable DCSH variable ordering (disabled by default, as for now considered experimental for end users).
• Improved data-based synthesis variable ordering documentation:
  • Added DCSH algorithm/option.
  • Extended explanation of heuristic algorithms in general.
  • Extended explanation of when algorithms are not applied.
  • Extended descriptions of the FORCE and sliding window algorithms.

This merge requests now builds on !333 (merged). Once that one is merged, this merge request will automatically be re-targetted to develop.

Addresses #196 (closed)