Separate TD functionality from DP/WIS

[bdsullivan]

Create standalone executable (main function) for elimination ordering and tree decomposition related tasks, separate from weighted independent set code. Care should be taken to avoid code duplication; move functions needed by both from max_wis files to appropriate library.

[bdsullivan]

This has been mostly addressed via new create_tree_decomposition wrapper functions (example usage in td_stats). Still need to go back and disentangle main functions for WIS (requires merge into master branch of wrappers).