Import/Export CSV

Might need to add the ability to import CSV files, depending on whether they've already used Excel to make their inventory.
This is a serious nitpick, so feel free to ignore it.  I personally like to not reuse variable names, to avoid confusing my simple-minded brain. In this code, location means the location name string, until we load the Location from the database, and then it's an ActiveRecord object.  Not the worst thing ever, and definitely easy to figure out in this short block of code, but there you have it, my pedantic and pointless complaint.  Other that though, this code is looking nice and clean, and more importantly than any of that - it actually works.  Awesome.