mpirun --help output revamp

This commit modifies the output from the mpirun --help
command.  The options have been split into groups, to
make the output smaller and more readable.  The groups
are: general, debug, output, input, mapping, ranking,
binding, devel, compatibility, launch, dvm, and
unsupported. There is also a special "full" command
that can be used to get the old behaviour of printing
out all of the options.  Unsupported options may only
be seen with this full output.

This commit also adds a special case for the help
argument.  It makes it possible for the user to
enter 0 or 1 arguments instead of having to always
enter an argument.  This defaults to printing out
the "general" help options so the user can then
see what help arguments there are.

Signed-off-by: Nathaniel Graham <[email protected]>

Author: Nathaniel Graham