db: Fix up some index names
db: Fix up some index names

In the images table, due to some columns having been renamed at various
times, their index name was still their previous column name. I think it
makes sense to keep the index and column names the same.

Signed-off-by: Andrew Clayton <02e0a999c50b1f88df7a8f5a04e1b76b35ea6a88@opentechlabs.co.uk>

ac000/receiptomatic