Update known issues document, including Fusion widgets that will not be ported across
Update known issues document, including Fusion widgets that will not be ported across

Fixes #480

jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout