relax SVN archive

Added some missing imports.

The spectrum_type arg is now propagated all the way to where it's needed.

Added a check to assign_function() for when the spectrum_type arg is incorrect.

Converted the assign_function() method to the new design.

Fix for the noe.py system test script.

The spin names needed to be set to 'N'.

Fixed the noe.read() user function.

Fix for bug #12418 (https://gna.org/bugs/?12418).

This bug was reported by Tyler Reddy <TREDDY at dal dot ca> in the post to the relax users mailing
list, https://mail.gna.org/public/relax-users/2008-10/msg00011.html (Message-id:
<20081007144810.ab985qup4408wokg@...>).

The problem was found by using an intersection technique, jumping between working and non-working
revisions until the exact patch was found. The issue is that the write() method expects more
arguments than it is getting.

Fixed all the references to the shifted system test data.

Removed the empty system test data directory.

Shifted the last of the system test data into the test suite common data directory.