relax SVN archive

The user function wizard pages now have an on_back() method which unregisters the observer.

This is needed as going back previously did not unregister the observer the object, hence going
forwards after going back would fail.

The wizard now has an on_back() method available to perform actions when going back.

The on_next() method has been fixed in that it is called even when the page is skipped.

Activated the apply and skip buttons in the relaxation data GUI element data reading wizards.

The relaxation data GUI element 'add' buttons now launch a multi-page wizard to input metadata.

The relaxation data 'Add' and Bruker 'Add' buttons now launch wizards whereby the first page is the
original relax_data.read or bruker.read user functions, but then this is followed by the
relax_data.peak_intensity_type, relax_data.temp_calibration and relax_data.temp_control user
functions. This allows the metadata to be set up prior to the model-free calculations.

The relax_data.delete user function now removes all of the metadata associated with the ID.

Changes to the relaxation data GUI element button layout.

The buttons are now all of the same width, and the metadata button is now last.

The relaxation data GUI element now has a button for opening the relaxation data metadata element.

This 'View metadata' button will launch the new Metadata_window wx.Frame. This window contains the
relaxation data metadata GUI element stretched to fit the window.

Fix for the relaxation data metadata GUI element for when no relaxation data exists.

The element no longer fails if data is absent.

The relaxation data metadata list GUI element now can stretch to fill the parent, if asked.

This will be used when the list is embedded within a window by itself.

Created a GUI element for displaying and editing the relaxation data metadata.

This is very similar to the relaxation data list GUI element, and it will be used in the BMRB export
(and maybe in a window launchable from the relaxation data GUI element itself).