edit notes file
abstracting the image library's file system usage from the UI code
added PDImageHost_NoPreview option
merge image library Did{Import,Remove}Files notifications into one
minor change to PDImageLibrary -importImages: method name
removed import UI file chooser, redundant as dest folder can be selected
simplify error recovery code in -[PDImage movedToDirectory:error:]
clean up PDImageLibrary creation (e.g. hide -init methods)
pulled image library catalog code into its own class