PR for the chordal tree decomposition builder

[PhoenixIra]

Things to do:

• Correcting mistakes or bad formulation in comments
• Correcting style issues
• Copyright is missing
• squash branch for pr
• open PR

[PhoenixIra]

• adding theoretical background (found a paper with the algorithm and currently writing a time complexity analysis)

[PhoenixIra]

Can someone help me squashing the branch chordalDecompositionPR for me? I struggled with this a bit...

[PhoenixIra]

I created the PR: jgrapht#616

[PhoenixIra]

I would like to have this issue open until the PR is finally accepted/rejected similar to the interval graph PR Issue