hdf5doc

Throughout doc set:
    Updated copyright notices.
    Updated release tags to 1.8.0-beta.
    Fixed broken or inappropriate links. 
    Made minor edits for revised doc set structure in Release 1.8.
    Migrated hdf.ncsa.uiuc.edu links to hdfgroup.org or hdfgroup.uiuc.edu, 
        as appropriate.
    Updated Help Desk links to point to THG and changing mailto URLs to 
        an image or spelled-out text ('help' at hdfgroup.org).
    Changed NCSA and NCSA-HDF logos to THG iconography.
    Added relevant files to Makefile.ins and MANIFEST. (1.6 only; not 1.8)
    Added RD100, THG logo, and Help Desk email imagery in Graphics/.
    Fixed broken HTML and other minor copy edits.
Tested:
    Firefox