The Pathhandler is used to convert paths with the ~beta notation to absolut path names.
It has the following attributes:
BetaLib: returns the path to the installation of the Mjølner System.
CurrentDirectory: returns the working directory.
ConvertFilePath: converts a "relative path" relative to a basic and returns the absolut path.
LocalPath: Given a path and a basis, exit the local path relative to the basis, if possible.
The FilenameConverter is a subpattern of the pathhandler. This
pathhandler is capable of keeping track of files which have allready
been "converted". ConvertFilePath will return the same pathname every
time the same file is accessed even if the absolute path-names
See the Interface file for details.