Modifying routines to remove hardcoded lines to have magnetic field information (name, characteristics, etc.) as entry

Fixing the legendre polynom to properly calculate the exoplant tilted magnetic field models TDS and proxima centauri

Adding all points of magnetic field lines (bx,by,bz,x,y,z,) along the whole magnetic field line asked by the user

Sync develop with master

See merge request !5

Gitlab ci

See merge request !3

Adding keywords into read_mfl routine to obtain the magnetic fields, f_ce, etc. along the magnetic field line

Changing the routine to a function. Adding L_shell keyword to be able to calculate L_shell or M_shell, depending on the magnetic field model which is called

Adding a routine that allow to calculate and plot the magnetic field map at the surface (longitude vs. latitude)

Adding proxima_centauri magnetic field model (based on http://dx.doi.org/10.1051/0004-6361:200810491)

Adding prompt command to ask the user for the apex value of the moon (in addition to the moon name), if the keyword moon has been set to 1 (rather than the name of a moon)