relax SVN archive

Changed some imports in preparation for support for different NMR-STAR versions.

Code rearrangement.

The BMRB read(), write(), and display() methods called by the user functions has been shifted to
generic_fns. This allows bmrblib to be purely a package providing an API for the NMR-STAR
dictionaries, with reading and writing done by pystarlib.

Shifted the tag name prefix creation code into bmrblib.tag_category.TagCategory.

Created the heteronucl_NOEs and heteronucl_T2_relaxation saveframes.

Created the T1 tag category.

Further object simplifications.

The __init__() methods have been shifted into the TagCategory base class in bmrblib.tag_category.

Code simplification by placement of many objects into the saveframe namespace.

Created the unused HeteronuclT1Software tag category class.

Created the HeteronuclT1Experiment tag category object.

Split up the T1 saveframe object.

The main object is now called HeteronuclT1Saveframe. The HeteronuclT1List tag category has been
shifted into its own object, and the other tag categories will be created next.