relax SVN archive

Switched to using os.popen3 for executing Dasha.

This allows STDOUT and STDERR to be caught and sent to relax's STDOUT and STDERR. Hence Dasha's
output is caught by the system tests, etc.

Fix for the extract() docstring.

Fix for the extract() method. The current data pipe was missing.

Fixed the creation of the Dasha script.

Fixes for the copy() and read() functions.

The specific set() function was destroyed at r4822, well at least shifted to
generic_fns.value.set_spin_params().

Converted the extract() function to the new design.

Converted the execute() function to the new design.

Created the 2 new API functions: first_residue_num() and last_residue_num().

Converted the create_script() function to the new design.

Converted the create() function to the new design.