* Renamed the 'defitintions' table to 'server_definitions' to clarify the purpose, and made all the 'server' columns have then 'not null' constraint.
* Created Database->insert_or_update_servers(), ->get_servers(), ->insert_or_update_server_definitions() and ->get_server_definitions().
* Updated scancore, anvil-daemon, and scan agents to not run unless they're run with root privs.
* Got scan-server to update the servers / server_definition tables and the on-disk file when needed.
Signed-off-by: Digimer <digimer@alteeve.ca>