[josm_plugins] update classpaths, fix various Eclipse projects of some plugins to have a consistent and errorless environment across all plugins (easier for JOSM developers to help plugins authors or update unmaintained plugins). Please do not revert these changes.

git-svn-id: http://svn.openstreetmap.org/applications/editors/josm/plugins@30124 b9d5c4c9-76e1-0310-9c85-f3177eceb1e4