Prefix-based per-RPC server configuration

If a process runs multiple RPC servers, there is no way to individually set their IPC parameters beyond what's supported by the RPC Builder. If a configuration is shared among many nodes, this is more problematic.

In this jira, a prefix-based per-server configuration is proposed. When an RPC server is built, a prefix can be specified, which will then be prepended to keys when retrieving configured values. There will be an option to fall-back to using the key without the prefix when no value is found with the prefix, thus making this feature compatible with the current way of configuring servers.