[BUG] GroTop parser fails when position restraint include directives are present

[lohedges]

The presence of include directives such as the following cause the parser to fail with no informative error.

#include "posre_0001.itp"

These files are written by BioSimSpace for when setting up a GROMACS system using position restraints. As such, the system can't be recovered from the topology and coordinate files without first removing these directives.

We could probably ignore this while parsing, but I'm not sure of the best approach. The itp extension is used for other includes too, so we can't just ignore that. BioSimSpace does always write using the same format, i.e. #include "posre_XXXX.itp``, so we could probably just match posre` in the include?

I'll open a fix branch for this.