Revision 758

(Projection): Removed Set*() methods to make
        Projection an immutable item. Fixes RTbug #1825.
(Projection.__init__): Initialize instance variables here.
(ProjFile.Replace): New. Replace the given projection object with
        the new projection object. This solves the problem of needing the
        mutator Projection.SetProjection() in the ProjFrame class and
        allows a projection to change parameters without changing its
        location in the file.