menu extension for last recently used files menu
functionality:
it is created with a link to the (file-)menu,
if it is created it is reading its content from config information
the add entry method adds a specific filename to the list, ensures that it
bubbles at top of list if it is already member of list
typically called by SaveFile method
LRU is added at the specific position at creation time
and all entries are going to be inserted or deletied
This method creates a project from the specified URL
Unlike the constructor which forces an .argo extension This
method will attempt to load a raw XMI file
This method can fail in several different ways.