hdf5doc

Description:
RM/Tools/h5repack.htm
    Add missing options:
        -u, --ublock
        -b, --block
        -t, --threshold
        -a, --alignment
    Fix incorrect options:
        -m number, --minimum=number
        -e file, --file=file
    Light edit:
        -M size, --metadata_block_size=size
    Fixes JIRA HDFFV-8020.
Tested:  Will be tested with Firefox/Safari as served from website.