relax SVN archive

In the GUI the userfunctions sys_info() and time() are now grouped into a "system" subclass.

This is to prepare for other system related functions.

Fix for the Structure.test_read_pdb_internal3 system test.

With the new atomic position concatenation support, when called sequentially the
structure.load_spins user function should always use the same value for the ave_pos argument.

Added support for concatenating atomic positions in the structure.load_spins user function.

Together with the spin_num flag set to False, this allows for atomic positions to be read from
multiple homologous structures with different PDB atomic numbering. The spin containers will be
created from the first structure, in which the spin is defined, and the atomic position from
subsequent structures will be appended to the list of current atomic positions.

Added the spin_num boolean argument to the structure.load_spins user function.

Setting this flag to False will cause the spin number information to be ignored when creating the
spin containers. This allows for better support of homologous structures but with different PDB
atom numbering. The default flag value is True, preserving the old behaviour.

Created a short Info_box copyright string for displaying in the main GUI window.

This shows the full range of copyright dates.

Updated the copyright notices for 2016.

Copyright update for the previous commit.

Bug fix for the structure.read_pdb user function (bug #24300, https://gna.org/bugs/?24300).

When the merge flag is True, and both multiple structures and multiple models are present, the
structure.read_pdb user function would fail with a RelaxError. The problem was that the molecule
index was simply not being updated correctly.

Creation of the structure.delete_ss user function.

This simply resets the helices and sheets data structures in the internal structural object to [].

Added a check for the total argument for the frame_order.distribute user function.

The maximum value is 9999, as the PDB format cannot accept more models.