Changes

* Improvements for a number of GUI elements used in the user function windows. * The ^[[?1034h escape code should now no longer be emitted by GNU readline on Linux systems. * Created the very basic structure.com user function for calculating the centre of mass. This is to simply allow an easy interface to the pipe_control.structure.mass.pipe_centre_of_mass() function. * Expansion of the REMARK section of the PDB file created for the internal structural object. This is visible when using the structure.write_pdb user function, as well as the many other user functions which create PDB files. The relax version as well as the file creation date are now recorded in the PDB file. This extra information should be very useful. Empty lines in the REMARK section improve the formatting.