hdf5doc

Description:
    Updated for 1.8.0 Beta 3
    Added mention of the new "format compatibility" document (with link)
        and the coming "API compatibility" document.
    Removed section describing features still to be implemented for 
        the release.  None of the features described will be in 1.8.0.    
    Edited introductory paragraphs accordingly.
    Began reordering feature list to align with the "format compatibility"
        document.
Tested:
    Firefox