Harvests

A few small tweaks based on customer feedback on the mailing list:

- added more units (cups, quarts, bushels, etc)
- added "harvest this" link to crop page
- added link to "all skud's harvests" from harvest detail page (and fixed/added similar links in plantings and seeds)
- turned quick links on homepage into a button bar for improved visibility
- removed duplicate edit buttons on harvest/seed/planting detail pages

PT for main harvests story: https://www.pivotaltracker.com/story/show/37282255