Includes sample variogram as output in gstatModel object. Added plot functionality for sample and model variograms.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/gsif@148 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Improved 2D variogram fitting.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/gsif@149 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
changed gstatModel class definition to allow sample variogram to be stored in output. representation function replaced with slots=c(...).

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/gsif@150 edb9625f-4e0d-4859-8d74-9fd3b1da38cb