Add features to MariaDB Monitor discover-replicas and bootstrap commands

Modify the existing discover-replicas command as follows:
1. No manual server names, only autogenerated names are supported.
2. Add option to remove servers that can no longer be discovered. If these servers are not used in any filter or service, they will be removed from both the monitor and from MaxScale itself.

Add bootstrap command. This command only works on an empty monitor and takes an address and a port as arguments. It then connects to the given address and scans the replication setup. If the discovered topology looks like a normal primary-replica setup, add the servers to MaxScale and the monitor, with discovered names.