[script] fix bug in execution Python script for long string of filepath

Python execution fix for long filepath :

• TelemacCas class has been modified (and existing method - contains_multiple_line - has been fixed) to handle long filepath on multiple lines (without mistake with commentary lines). It is based on some assumptions (number of "'", commentary line begins by "/", etc.). It looks robust (on Telemac-Mascaret exception) but it may remain some exceptions.

(this branch should correct the problem of long pathfile in Q4TS @jean-marie.kerloch)