Respect original topology headers/preprocessing options

[ijpulidos]

When dealing with the insane.py script I noticed that when solvating a CG protein with

insane -o system_solvated.gro -p system.top -f system.gro -sol W -salt 0.15 -center

The headers of the original system.top file are ignored and then just simply changed to #include "martini.itp". I think insane.py should respect the prevopis original header or preprocessing options, for example including different martini specifications files or specifying custom system itp files.