Additional hacky addition to deltaDTD to ensure that we are removing any year that contains one month with NA > max_NA

There was some fear that my function (now called solar_daily) would confuse folks looking for the original research paper and code. As such, I've purged references to the old function name to minimize the chances of a search engine leading folks here instead of to the original author's work.

Signed-off-by: Conor Anderson <conor@conr.ca>