#13: Debug incorrect reported values of W when beta is non zero

[ppebay]

Fixes #13

• also adds sanity checks (between $\psi$ and $\chi$
• improves printouts for clarity of results

Specifically for python ccm_milp_full.py -c ../tests/config/1-fwmp-with-alpha-beta.yaml, the obtained configuration:

now gives the correct values for W:

# Solution summary:
Rank 0: L = 2.5, W = 4.0, unhomed: 1
Rank 1: L = 1.5, W = 4.0, unhomed: 1
Rank 2: L = 2.0, W = 4.0, unhomed: 1
Rank 3: L = 2.0, W = 4.0, unhomed: 2

[maxime-bfsquall]

I just make a commit for pylint issue but nothing else to report