Create growingrecs.py

Command-line tool to find the most common planting conditions for a given crop. This version counts combinations of planted_from and sunniness, but as planted_from is often left blank this may not be the best choice.
BSD license was what I chose for the github repo.  It might be good for us to develop some suitable boilerplate to go at the top of each script, with links to the github, license, and other info. Not urgent, just a thought.