Make minor changes to the DB comments and args
Separate DB testing from main routine

This adds a flag (--testdb) which creates a temporary sqlite3 database,
runs tests on it, deletes it, and terminates. This prevents entries from
being added and removed from the configured database on every startup.
Implement --debug flag and set default log level

By default, only log messages with importance INFO or more severe will
be shown. Debugging messages can be shown with --debug.

Also, the message listing number of nodes in the database, which is
printed at startup, is now INFO rather than DEBUG.
Add ReadOnly mode and make it default in the conf

ReadOnly mode is part of a database and is specified either in the
configuration or by command line flag. If either the flag --readonly or
the Database.ReadOnly option in the configuration is set to true, the
API will not allow database operations. This only applies to the API.

Additionally, the example configuration has been changed to bind on all
interfaces again, because ReadOnly is true by default.