See if it's feasible to implement parallel processing for calc_palmsplus

[TheTS]

Try and foreach this loop. If significant speed improvement, parameterise parallel_processing

  for (i in unique(data$identifier)) {
    x[[i]] <- data %>%
      filter(identifier == i) %>%
      mutate(!!! field_args) %>%
      mutate_if(is.logical, as.integer)

    if (verbose) {
      cat("[", j, "/", len, "] Computed palmsplus for: ", i, "\n", sep = "")
      j <- j + 1
    }
  }

[TheTS]

Note: a quick test is ~300% faster on 7 vs. 1 core. Tricky to implement as palms dataset is copied to each worker (too much RAM). Also, to keep field tables dynamic, the global environment needs to be copied too.

Not a massive deal as < 6 min for 194 identifiers.

Might revisit this in future (and for palms_build_trajectories too).