Open all models in a PDB file
Open all models in a PDB file

Currently BALLView only opens the first model in a PDB file. This patch
loads all models contained in a PDB. Ideally there should be a dialog
which can be used to control the models loaded, but this is better than
nothing

tkemmer/ball,tkemmer/ball,tkemmer/ball,tkemmer/ball,tkemmer/ball,tkemmer/ball