relax SVN archive

The isotope number is now being guessed from the atom name if not given in the BMRB file.

The molecule number from EntityID is now being used to fill in the model-free data.

This is necessary for multiple molecule entries in BMRB files.

The Python round() function is now used to create the MHz frequency label for the relaxation data.

Expanded the conversion of Modelfree4 model numbers to include all of the relax model numbers as well.

Added a catch to _bmrb_model_map() for Modelfree4 model names in the BMRB files.

Fixed the print out of a RelaxError and Warning for the model-free model from the BMRB file.

Fixed a RelaxError in _model_map() so that a model-free model of None will raise the correct error.

Model-free saveframes without any data are now skipped.

The BMRB generate_sequence() function can now handle args of None.

The BMRB generate_sequence() function can now handle if no molecule name is given.