New generic 'relrisk' with methods for 'ppm' and 'ppp' (and bugfixes).

   ppmclass.R
   model.matrix.ppm.Rd
     model.matrix.ppm and model.matrix.kppm have new argument 'Q'

   quadscheme.R
     Buglet fix in quadscheme.replicated
     ('sourceid' was incorrect if dummy pattern was empty)

   relrisk.ppm.R [New file]
   relrisk.ppm.Rd [New file]
   relrisk.Rd -> relrisk.ppp.Rd
   relrisk.Rd [New file]
      relrisk is now generic with methods for ppp and ppm.

   NEWS
   DESCRIPTION
   updates.Rnw
      updated.