Production push: harvest improvements, more RSS, crop uploads, new garden fields

* Crop CSV upload: load arbitrary CSV files of crops eg. as created by crop wranglers, from the command line.  A CSV of pepper varieties has been added to db/seeds
* Harvest improvements: various small tweaks
* New garden fields: inactive, size, specific location
* More RSS links: posts and comments now have RSS links at the bottom of the page
* Dev improvements: better_errors in dev, subdue heroku warnings, refactor Crop.system_name to Crop.name

Note: on production push, make sure to run:

    rake growstuff:import_crops file=db/seeds/crops-10-peppers.csv