relax SVN archive

Fix for the print_frame_order_2nd_degree().

The NaN fix was partly incorrect.

Fixes for print_frame_order_2nd_degree() for when NaN is encountered.

Renamed the state.load() and state.save() directory argument from dir_name to dir.

This is to bring it in line with the rest of relax.

Added a dir arg to a state.save() call in test_state_pickle().

Changed the default save state to XML.

Fixes for load_pickle().

The ds.__reset__() call has been removed because of redundancy and the new ds.is_empty() has been
blacklisted.

Duplicated the test_state() system test into test_state_pickle() and test_state_xml().

This tests both formats.

Added the force flag to the state.load() user function.

When True, this causes the relax data store to be reset prior to state loading.

Updated the relax data store from_xml() method for support of the loading of the XML state file.

Docstring clarification of the dir arg.