Use Guava 11 in GoRPC lib

We've been using Guava 18 which is not backward compatible with the
version 11 used by Hadoop core. Downgrade to avoid version conflict.
Use maven shade plugin to generate jar with dependencies

FieldType VT_VAR_STRING (varbinary and varchar) should be casted to byte array instead of String
Use Guava11 to avoid version conflict with Hadoop
VtGate Java Client: Add ExecuteBatch API call

ExecuteBatch lets multiple queries to be executed in single round trip
to the server.