Added few documentation

IDS/gen_filament.m

 function  [discretizationr, discretizationz, Twc] = gen_filament(vvdata, num, type_coil_description,varargin)
-% Generate filamentary(windings) discretization from different geometrical coil descriptions
+% Generate filamentary(windings) discretization, and grouping matrix, from different geometrical coil descriptions
 
 % type_coil_description = 2 -> rectangle description
 % type_coil_description = 3 -> oblique description