relax SVN archive

Complete rewrite of the add_r1_1() method, now called peak_list_add_action().

This includes:
- The proper support for multiple file selections.
- Checks for too many peak lists.
- A new method called count_peak_lists() added.
- The refresh_peak_list_display() method written to update the GUI element at any time.

Updated the multi_openfile() function.

The args were turned into keyword args, the function comments converted to a docstring, many comments
added, whitespace fixes, and dialog.GetPaths() is now used to return a list of files.

Created the gui_bieri.message.error_message() function for displaying general errors.

Converted the peak list button from text to bitmaps.

Imported the 48x48 icons.

Shifted the peak list button sizes into one local variable, 'size_button'.

Added the 48x48 icons to the icon paths.

Added a few icons for addition and removal of data.

Fix for sync_ds().

The relaxation times were not converted to proper strings.

Initialised the list_file and relax_times data storage variables to be populated with ''.

The length is set to the hardcoded value in self.peak_list_count.