relax SVN archive

Converted Scientific Python from a dependancy to an optional Python package.

Of course since this is the only PDB parser in relax at the moment, if Scientific Python is not
installed, then PDB files cannot be read.

Spun out the Scientific Python specific code into its own module.

Fixed a typo causing several unit tests to fail.

Removed many unused imports.

Added 2 unit tests for the new args of the structure.read_pdb() user function.

Added a missing RelaxError import.

Fixed the test_read_pdb_argfail_load_seq() unit test.

Fixed all the 'structure' user functions to use the new package.

Converted the 'structure' package into a subpackage of 'generic_fns'.

This solves a module import issue, and is a logical place for the code.

Added the 'geometric' module to the __all__ list.