BK-432: Ignore insert images that exist

[thomasbrockmeier-ams]

• Updates SQL statement to fill images table to ignore errors when a record exists.
• Changes function that handles database connection to a context manager to guarantee connections being closed, both on a successful execution of the scripts, as well as on failure. This prevents the accumulation of dangling connections on the database.
• Some refactoring to attempt to make the distinction between inserts to the images and detections tables clearer.
• Changes database connection to autocommit since we are committing immediately after generating a SQL statement anyway. Should also prevent long running connections/table locks when the program fails between uncommitted SQL statements.