relax SVN archive

The add_spin_systems() base class method now returns the Text_ctrl instance it creates.

More of the model-free auto-analysis GUI tab is disabled with the execution lock.

Converted the analysis base class add_text_sel_element() method to the object Text_ctrl.

This has the Enable, SetValue, and GetValue methods implemented as a wx object.

Renamed the spin_ctrl module to elements to store all of the special analysis elements.

More enabling/disabling of the model-free auto-analysis GUI element.

The user function and wizard buttons, and relaxation data list are now all responding.

The spectrum list GUI element can also now be enabled/disabled via Enable().

The relaxation data list GUI element can now be enabled/disabled via Enable().

All the model-free auto-analysis activation and deactivation calls now pass through wx.CallAfter.

This is to avoid racing.

The model-free model fields are now activated/deactivated with the execution lock.

Eliminated the add_spin_element() method and shifted to using the Spin_ctrl object.