Add 1MYK.pdb file

This adds the 1MYK PBD file which is used as an example for
the APBS extension to Avogadro.

Change-Id: I5259a0528bed77dc0caf21eab91321a7defaa951
Merge topic 'add-1myk-pdb' into master

580dcc41 Add 1MYK.pdb file