resource management
domMapWidget uses an optional resourceTranslator for images
content assigns unique resource postfix automatically
translate to pixel when calculating dimensions
resource translation for image dnd
set resource with a particular id
execCommand processing
event symmetric to command for storeResource
moved icon translation to insert controller to avoid dnd problems
reusing unique content
clean up unused resources on load
Revert "clean up unused resources on load"

This reverts commit aa51b1cd81af54d3edf41ce657793da86dd6e8b6.