Uniform code path for writing out console help.

Uniform code path for writing out console help.

Now both 'gmx help <module>' and 'gmx <module> -h' trigger exactly the
same code path, making things a lot easier to work with.
Some notable things:
 - Moved the responsibility to parse the -hidden argument into the
   wrapper binary, from where it gets passed down in
   CommandLineHelpContext.  Quite a few files are touched by this.
 - The -h option now causes all other options to the module get ignored.
   g_tune_pme requires some other approach to deal with option
   validation, but even adding a separate command-line option for only
   this purpose is probably better than the multiple code paths that
   were there before this change.
 - Related to the above, the help output could be significantly
   simplified, since it no longer depends on the command-line.
 - Removed the -verbose option that caused the options to be printed
   during a normal run.  Possible to add back if people want it, but it
   simplifies things if it isn't needed.

Related to #685 and #969.

Change-Id: Ibe735711f650eafaecf28ffb1ed92da97dcb81b6