[scripts] Add features to MascaretGeoFile and Section (1D) classes + code-style correction & docstring

Add features to MascaretGeoFile class :

• Reading topo-bathy information used for limits of minor/major beds in 1D profiles of Mascaret ("T" stands for topographic which means major bed of the river and "B" for bathymetry which means minor bed of the river)
• Reading sediment layers in Courlis geometry files (geoC & georefC)
• New method to generate GIS file formatted for PreCourlis QGIS plugin (attributes containing geometric information)

Modification to Section (class of mascaret_file.py) to store topo-bathy data

Adaptation of notebooks tests touched by those modifications

+ some coding-style corrections and add docstrings