relax SVN archive

The method is now passed into add_execute_relax() to allow derived classes to specify this.

Shifted the model-free add_execute_relax() method into the base class.

Generating new user function 'read_xyz()'.

This is Han's patch https://gna.org/task/download.php?file_id=13153 attached to the task
http://gna.org/task/?7404.

The user function 'read_xyz()' was generated and modified in the generic_fns/structure/main.py based
on the function 'read_pdb()'.

The add_mf_models() method is now using add_static_text() for the text.

The model-free model buttons now expand to the correct width.

Completely refactored the model-free model buttons code.

Removed references to the repository line 1.2 from the download page
(http://www.nmr-relax.com/download.html).

This follows a message by Edward at:
https://mail.gna.org/public/relax-devel/2011-06/msg00115.html
Message-id: <BANLkTikUSnMKJaOivCPwtB55P3QaEDry=Q@...>

Added a reference to the update of the repository code using 'svn up'.

Corrected an error in the html code.

-> Line 124, Column 9: end tag for element "tr" which is not open

This was pointed out by the W3C Markup Validation Service (http://validator.w3.org).

Added a section for the source code repository in the download page.

This follows a message by Edward at:
https://mail.gna.org/public/relax-devel/2011-06/msg00078.html
Message-id: <BANLkTimq=4vfngu+u2WBAuTTsS0nMW+B4A@...>