Keep uploads reverse index up to date

Meta: [Reverse index of user uploads](http://meta.discourse.org/t/reverse-index-of-user-uploads/6017)

- [x] 1051b8de84612b768f6384df8e442a685cf39e2b removed useless ignored directories
- [x] ae3543872c3415e66fd38dcf519f603d84d1d5c9 renamed the `upload`'s `sha` column to the proper `sha1`
- [x] 7bdc616040c934225e512e0e3eed27ab2b3404e6 keep uploads reverse index up to date