Martinate -cg could accept an ITP

[jbarnoud]

Using exotic versions of force fields with martinate is made difficult by how martinate expects the force field to be provided by name. The way to provide such exotic version of martini now is to create a custom martini.py script in the right directory. Being able to provide an ITP file to the -cg option would make the task much easier.

Allowing an ITP to be passed to -cg could bite us at several places, though:

• martinize will not like it
• if no solvent is provided with -sol, martinate tries to guess from the force field name
• the above point is especially delicate with dry-martini
• quid of multiscaling?