DefaultOpService: give more info when op not found
DefaultOpService: give more info when op not found

When there is no match, or multiple matches, it is really helpful to
know more information about what the system tried to do. Let's add this
information to the IllegalArgumentException so we don't have to keep
debugging it manually.

gab1one/imagej-ops,kephale/imagej-ops,stelfrich/imagej-ops,imagej/imagej-ops