File upload feature in admin page

File upload feature is now working! You can now attach images to your meals and they will show up in the admin page and the main page along with the recipes.

Known issues:
- Image file path doesn't update if you upload an image to one meal and then view another meal. The stale file path is cosmetic and does not affect what's in the database or the image preview. 
- If you create a new meal, save it, and then immediately try to edit it you will not be able to save it again. You have to click it in the meal list to get a "fresh" version. This shouldn't be hard to fix, and it's unrelated to file upload.