relax SVN archive

Wrote the Element.is_empty() method.

Added a unit test for the PipeContainer.is_empty() method.

Wrote the PipeContainer.is_empty() method.

Deleted the relax 1.2 save state (used in the results file reading system test).

Renamed the test_read_results() system test to test_read_results_1_2().

This is because the results file is in the 1.2 line format. Hence the results file has been renamed
as well. The loading of the 1.2 program state has also been axed.

Loosened the checks in the angles calculation system test to allow 64 bit platforms to pass.

Converted the return_units() function to the new relax design.

Converted the return_conversion_factor() function to the new design.

Added the dummy spin_id keyword arg to the map_bounds() function.

Reverted r5933, as this change was incorrect.

The command used was:
svn merge -r5933:5932 .