- adopted the plotting of ST*DF objects (all classes are corced to STIDF and a single method does the job)
- kml_layer now relies on slot "endTime" of ST*DF to define "TimeSpan.end"
- importFrom(sp, ...) in NAMESPACE missed a few things, changed to import(sp)

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/plotkml@486 edb9625f-4e0d-4859-8d74-9fd3b1da38cb