relax SVN archive

Bug fix for the generic_fns.sequence.validate_sequence() function.

Completed the generic_fns.sequence.read() function.

Renamed valid_sequence() to validate_sequence() and called it from within the read() fn.

Fix for the generic_fns.sequence.read() function.

Converted the strip class method to a module function.

Added the missing import of relax_io.strip.

Fixed the path in the unit test for reading a protein sequence.

Updated the extract_data() for the new relax design (converted from a class method to a function).

Started to implement the read, sequence_exists, and valid_sequence functions.

Small fix for RelaxInvalidSeqError.