Store details of Wirehead sessions in the database

[philpax]

Based on my current understanding of the genevo library, it is impossible to store and load the state of an existing session. However, that doesn't preclude storing the state that was used to initialise a session. This could be used to start it from the beginning, or to implement #59 properly: the custom IDs can include the ID of the session, which can be combined with the genome to reproduce the image exactly.