relax SVN archive

Fixed the call to the 3D isosurface mapping code.

The open_write_file force arg has been converted to a bool.

Fixed the calls to relax_io.open_write_file().

Renamed all refs to 'file' to 'file_prefix'.

Changed the 'res_num' arg to 'spin_id'.

Removed all references to 'run'.

Converted the map_space() base class method into the __init__() method.

Fixed a function vs. arg name clash.

Improvements to the dx.execute() user function.

Completed the run() function docstring.