I took care of the comments and merged. Thanks, Patrick, for enduring all of my
comments :-)

I had a look and left some final comments.

Patrick, Cedric and I are happy with the patch now. Malte, are you fine with the
changes (especially outside the option parser code)?

I left a few more comments. As usual, I'm more picky with the code outside the
option parser, but I think one of them looks like a genuine bug.

Great! From my point of view, this can be merged.

I incorporated the more comments

I left some more comments on Bitbucket.

Comments incorporated

I left some comments on Bitbucket.

The PR can be reviewed under:
https://bitbucket.org/PatFer/downward/pull-requests/11/issue844/diff

Whether or not a plug-in type supports predefinition and what the associated
command-line option is should be controlled by the user of the option parser,
i.e., by the PluginTypePlugin, not in the option parser code.

Parts of meta-issue issue588.