create standAgeMaps by default from cohortData

[achubaty]

We've been producing these after-the-fact for downstream users, using code like the following:

## make annual standAgeMaps from cohortData
  lapply(2011:2100, function(year) {
    cohortData <- qs::qread(file = file.path(resultsDir, paste0("cohortData_", year, "_year", year, ".qs")))
    cohortData[, bWeightedAge := floor(sum(age * B) / sum(B) / 10) * 10, .(pixelGroup)]
    cohortDataReduced <- cohortData[, c("pixelGroup", "bWeightedAge")]
    cohortDataReduced <- unique(cohortDataReduced)
    pixelGroupMap <- raster(file.path(resultsDir, paste0("pixelGroupMap_", year, "_year", year, ".tif")))
    names(pixelGroupMap) <- "pixelGroup"
    standAgeMap <- rasterizeReduced(cohortDataReduced, pixelGroupMap, "bWeightedAge", mapCode = "pixelGroup")
    writeRaster(standAgeMap, filename = file.path(resultsDir, paste0("standAgeMap_", year, ".tif")), overwrite = TRUE)
    TRUE
  })

We should produce these during the simulation - possibly in this module, or in another Biomass_ module.

[achubaty]

standAgeMapGenerator() was added to LandR in v1.1.1