One can now produce a Makefile.conf and a sourceme.sh
using autoconf. Just type:

./configure

Or maybe

./configure CXX=icpc

In case you want to use mpi, just use:

./configure CXX=mpic++

Everything should be smooth. I took care that the generated Makefile.conf
is compatible with those stored in configurations/. In this way,
one can always resort to a saved configuration file. Moreover,
jumping between git branches (without need of reconfiguring) will be
easier.

More info on the manual page (no need to use autoconf to compile
the manual and see that page)

Closes #46

It allows running plumed in a different environment from
where it was compiled (e.g. windows).

I added a PEOPLE file containing list of authors and a script
(src/header.sh) which applies the Licence to all the source files.

It can be applies multiple times (it automatically deletes the present header
and replace it with the new one). Thus, to change the header, edit header.sh
and execute it.

This is the draft version that I prepared and that we will use as
a starting point. Still it is a bit dirty, and I will try to improve
documentation and delete unused routines