[Distributed] Support metadata queries

Metadata queries, like "getNodeList", "getPathNextChildern", "getTimeseriesSchema" are currently unsupported. The point is that the paths being queried may contain wildcards or they may be prefix paths, which makes it a little hard to figure out which data groups to send the query.

The simplest way may be performing a broadcast and merge the results, which is clearly less efficient. I am hoping you can give a more brilliant idea to resolve this.