1 graph per solution => multiple graphs per solution files

Remove calls to python functions and replace them with much more efficient pure C functions

[cmd] Implement & Refactor the conversion of previous frontier places to numerical values => big perf gain

[lib] CLUnfolder: Fix error during the init of __invariant_constraints with dimacs data from query: extend instead of append

[gui] Form Checker: Fix typos; Add not() for invariant property (usefull to know this); Try to fix fields widths

[cmd] Add todo: need to put some functions of command_line tools into the cadbiom library (for the loading of macs...)