add hash function pool
Merge branch 'master' into shumo_add_more_seeds_for_hash_function
Merge pull request #581 from uwescience/shumo_add_more_seeds_for_hash_function

Hash function pool
Merge pull request #597 from uwescience/slxu-improve-sql-exception-processing

Process SQLException.getNextException
Merge branch 'master' into slxu-kill-query-at-aborted-downloading
SystemTestBase: up worker bootup timeout
Merge branch 'master' into slxu-fix-network-backpressure

Conflicts:
	systemtest/edu/washington/escience/myria/systemtest/SystemTestBase.java
Merge branch 'slxu-fix-network-backpressure' into slxu-kill-query-at-aborted-downloading
Merge branch 'slxu-kill-query-at-aborted-downloading' of https://www.github.com/uwescience/myria into slxu-kill-query-at-aborted-downloading
Add an explict short message type in IPC layer
Merge Data into StreamData
IPCMessage deserialization in one place

And deserialize short message types.
Process IPCMessage.StreamData and IPCMessage.Msg

Correctly processes the two types of user messages.
Do not move buffer pointer if msg is not Meta
Only IPCMessage instances are written into Netty

Wrap stream messages and short messages into StreamData and Msg
separately so that the IPC layer knows the data types.
Fix serialize part of the message handler

All messages written are now of IPCMessage types. Serialize the
payloads by the payload serializer, rather than the message object
itself.
Detect stream messages in non-stream channels

If a query fails, input channels will be released. There may be stream
messages received after the release. Drop them.
Misc code cleaning.