Openbabel 2 3 x

This is the additional support to HM spacegroup in possible allowed specifications  in .car format. HM spacegroup can be enclosed within parentheses and can contain space between them as per the given format details in -
http://hincklab.uthscsa.edu/html/soft_packs/msi_docs/insight980/formats980/ClassicFiles.html.
The current code which read .car format doesn't recognize such spacegroup as it strictly look for 8 fields
after tokenizing them using default delimiters as space, tab, newline.

It is legal to have .car files with PBC=ON and no space-group defined in the fifth line and just have PBC and a,b,c,alpha,beta,gamma parameters. Such structure is considered to have lowest symmetry space-group as P1. This means there are no symmetry operations in play and all atoms are explicit within the unit cell. The .car files for H2O and polymers fall under this category since they are amorphous but are periodic.

Added test case to exercise the change for such spacegroup format.