Mustang - improve namelist reading
In initMUSTANG subroutine MUSTANG_param, all readings are done twice to read the default value first and the user value after. This is done by copying each line of code.
Proposal: add a subroutine for reading to avoid code redundancy
The reading is done sequentially which means that the order of namelists is important in the file
Proposal: add rewind after each read to allow user to have list of namelists in any order