Merge 7 fixed functionality into master

man/validate_is_null_or_number.Rd

man/validate_is_null_or_numeric.Rd

man/validate_is_null_or_str_flag.Rd

man/validate_is_null_or_string.Rd

man/validate_param_list.Rd

man/validate_wrapper_list.Rd

man/xpaths_for_classes.Rd

tests/testthat/test-export_prj.R

tests/testthat/test-generate_benchmark_script.R

tests/testthat/test-generate_xml.R

tests/testthat/test-ogs6.R

tests/testthat/test-ogs6_ensemble.R

tests/testthat/test-prj_time_loop.R

tests/testthat/test-read_in_prj.R

tests/testthat/test-read_in_utils.R

tests/testthat/test-sim_utils.R

tests/testthat/test-utils.R

tests/testthat/test-vtu.R

vignettes/dev_workflow_vignette.Rmd

vignettes/user_workflow_vignette.Rmd