Revisit whether Warnings or Errors are most appropriate for bad_sites in occDetFunc()

[drnickisaac]

occDetFunc() performs several checks to compare the sites in occDetdata with regional_codes, and to check that each site is in exactly one region. There are four such checks for mismatches. In previous versions two of these tests returned an error and two a warning. In v0.2.09 all four of these return a Warning, and sites that don’t conform are dropped from the analysis. This is after the check for whether the data are sufficient to fit a model, so it’s possible to produce a sensible-looking model from only a subset of the data (and falling below the data threshold set by criterion). In previous versions at least two of these returned an error. It would be worth re-evaluating whether a Warning is the most appropriate behaviour here.