refactor the ErrorMarkerUtils APIs a bit, add the ability to show the
tooltip upon click.

remove some unecessary depenendencies from the gui-util package to
facilitate reuse.

add a new ErrorMarkerUtils pattern that simplifies adding markers and
gathering the messages for the markers (currently only used in external
ISAAC Knowledgebase Artifact Publisher code) but will refactor hear at
some point.
just a reminder comment
remove a dependency that appears unneeded at the moment, and triggers a
nasty bug in maven 3.2.2 that breaks the build....