added documentation
removed orphaned IBIS module
added .nc files for testing to utils/inst/extdata; updated test.settings.xml
deleted utils/R/variance.R, which was exact duplicate of modules/uncertainty/R/variance.R; updated DESCRIPTION / NAMESPACE files
added test for model2netcdf.BIOCRO.R; updated tests and examples for PEcAn.BIOCRO; worked toward matching BIOCRO output with model2netcdf.BIOCRO