DRILL-4728: Add support for new metadata fetch APIs
+ Protobuf messages
- GetCatalogsReq -> GetCatalogsResp
- GetSchemasReq -> GetSchemasResp
- GetTablesReq -> GetTablesResp
- GetColumnsReq -> GetColumnsResp
+ Java Drill client changes
+ Server side changes to handle the metadata API calls
- Provide a self contained `Runnable` implementation for each metadata API
that process the requests and sends the response to client
- In `UserWorker` override the `handle` method that takes the `ResponseSender` and
send the response from the `handle` method instead of returning it.
- Add a method for each new API to UserWorker to submit the metadata work.
- Add a method `addNewWork(Runnable runnable)` to `WorkerBee` to submit a generic
`Runnable` to `ExecutorService`.
- Move out couple of methods from `QueryContext` into a separate interface
`SchemaConfigInfoProvider` to enable instantiating Schema trees without the
full `QueryContext`
+ New protobuf messages increased the `jdbc-all.jar` size. Up the limit to 21MB.
this closes #527
