New functions, and their HELP text

 EQNSTATE2 - Matlab implementation of QUODDY's Equation of State.
 ICQ4INFO - GUI display of .icq4 file contents
 PLOTDROG3 - plot 3D drogue .pth file output from DROG3D or DROG3DDT.
 READ_ICQ4 - read a QUODDY4 .icq4 file
 READ_PTH - read drogue .pth file output from DROG3D or DROG3DDT.