fixed some bugs when processing files with the new module method; startet to built a common super class for File/Directory Definition; filedef is already partially on it
made the File/Directory "Definitions" to "Descriptions" -- suits them better; also DirectoryDescriptions now inherits from BaseDescription
now we have a namespace, we can make FsInventory to Fsinv::Inventory
lookuptable has an empty? method now, and the tabs will only be in the to_hash of an Inventory if they are not empty