relax SVN archive

Added a unit test test_set_n_state_model_rx() for checking value.set() with the N-state model.

Created the arg_check.is_list() function.

Fix for the generic_fns.value.set() method.

The return_data_name() specific API method should have been used to send the correct string into
default_value().

Created the common API method _set_param_values_spin().

A number of modules are now using this method.

Added the api_common module to the __all__ list.

Created a module for storing API methods common to different analysis types.

Added 'HH' and 'HZ' to the amino acid atom names in __det_pdb_element().

This is in response to Tiago Pais's <tpais att itqb dot unl dot pt> post at
https://mail.gna.org/public/relax-users/2009-11/msg00002.html (Message-id:
<AF0E494FAE984C0BB8D4C8CE521D621D@...>).

Fix for the call to set_param_values().

Fixed a typo in the new generic_fns.value.set() function.

Deletion of the set_non_spin_params() method.

This mess is no longer in the base API.