This set of changes impliments the following:

This set of changes impliments the following:

- FG now directly supports Robin's native nav database file format.
- His latest data now separates out dme, gs, loc, and marker beacon
  transmitters rather than lumping them all into a single "ILS" record.
- These new data structure changes prompted me to do some code restructuring
  so that internally these different types of navaids are all kept as
  separate lists and searched and handled separately.
- This structural change had a cascading affect on any code that
  references or uses the nav databases.  I've gone and "touched" a lot of
  nav related code in a lot of places.
- As an added bonus, the new data (and code) adds DME bias so these will
  all now read as they do in real life.

- Added Navaids/navdb.cxx and Navaids/navdb.hxx which provide a front
  end loaders for the nav data.
- Added Navaids/navrecord.hxx which is a new "generic" nav data record.
- Removed Navaids/ils.hxx, Navaids/ilslist.cxx, Navaids/ilslist.hxx,
  Navaids/mkrbeacons.cxx, and Navaids/mkrbeacons.hxx which are all now
  depricated.