relax SVN archive

The relaxation file names are now scrolled all the way to the right in the auto model-free tab.

This allows the file names to be seen better.

Improvement for the File_selector class, the file name is now scrolled all the way to the right.

This is inside the wx.TextCtrl field.

Created a base class file selection widget for the user function windows.

This includes a special class, File_selector, for handling the wx.EVT_BUTTON events and updating the
field.

Added a rough graphic for the sequence user functions.

URLs in the about windows are no longer italicised or underlined.

Bug fix for the spin view window - the tree view is not updated by the toolbar before it's built.

The relax controller and spin view windows are created when first called, saving significant start up time.

Fix for the half hidden about gui window - the virtual size is now the maximum of x and y.

The titles are now properly centred.

The temporary DC is now a wx.ClientDC as a wx.PaintDC should only be used in a EVT_PAINT!