relax SVN archive

Added the structural API base class method num_str().

This base class method is not a stub, but returns the length of 'self.structural_data'.

Prepared for a new structural API method, num_str(), for counting the number of structures.

Fix for extract() to handle residue misalignment between mfout and the relax data store.

Fixed all the calls to get_mf_data().

Fix for the get_mf_data() function.

Fixes for the extract() function.

Reintroduced the test for the model-free model but with a RelaxError now thrown.

This test was important as the model is necessary to differentiate between te and ts in the mfout
file!

Removed the tests in extract() for the presence of a model-free model and relaxation data.

These tests reduce flexibility as these can be set later, and the reading of the mfout file does not
depend on these.

Fixed the call to line_positions().

Converted the line_positions() to the new design.