Wrap-up
Removed timestep column.
Added the json files to ingest some of the snapshots.
importDataset: require workers to be set, and and allow overwrite
Server: make shutdown succeed if not started

basically, just closes the Catalog
MasterDaemon: if starting the API Server fails, shutdown server
MasterApiServer: support SSL

If the right values in the API are configured.

See: https://github.com/uwescience/myria/wiki/Myria-REST-server-SSL-support
Server: another safeguard against zombie queries
protobuf: add subquery ID to control messages

There will be a subsequent commit to make the server and worker control
structures handle this well.
parallel: many cleanups

Switch from long queryID to QueryTaskId taskId, as prep work for
subqueries.

This commit also refactors some logging statements to not construct
strings, but rather use the printf-style formatting that is more
efficient. The LOGGER.ifBlahEnabled() checks are also removed when they
are not more efficient (i.e., the logging command does no complex
operations and hence no work).

Also remove QUERY_PAUSE and QUERY_REMOVE from Myria, as these are never
called. In particular, the IPC utility to generate a pause message from
the server is never called.
operator: add DbReader and DbWriter interfaces

This enables operators to advertise that they read or write relations.
Catalog: simpler interface to set query status

always require a QueryStatusEncoding; make users construct one if they
want hand coded strings.
QueryExecutionStatistics: return null if not started, elapsed after

If not started, return null for elapsed.

If started and not finished, return elapsed since start.
build.gradle: upgrade guava
QueryEncoding: use FTMODE, not string

It actually does the right thing with enums.
QueryConstruct: refactor slightly

Option 1: plans and options come in at the same time (QueryEncoding)

Option 2: plans and options come in separately (Fragments, then options)
DatasetStatus: add deserialization annotations

So we can turn at JSON string into a DatasetStatus if need be.
SystemTestBase: helper functions to get dataset/query status from response

And then use this to extract query id rather than hard coding it
QueryConstruct: use LOGGER, not syserr
myria: cleanup use of Attachmentable

It's not used at all by the OperationFuture classes, and it was
implemented wrong by the AttachmentableAdaptor.