Change logging backend of SLF4j from Logback to Log4j for better compatibiltiy with YARN.
We'll still ship the Logback configuration file and pass them their path to the JVM so that
users can use Flink with Logback as well.

This closes #125
Removed slf4j-simple dependency from streaming component.
Fix Bug in ScalaAggregate Operator and add ITCase
Change Partition Operator to actual general-purpose Operator

It is no longer a special-case operator that can only be used in front
of map-style operations.
[FLINK-1123] Add first-n to Scala API
[FLINK-1120] Add Explicit Partition/Rebalance Operator for Scala API
Update doc with Scala First-N and Partition/Rebalance
Added TPCH query examples for Scala API
Improved Java TPCH query examples
Removed RelationalQuery Java API example
[streaming] Added CoBatchReduceInvokable, CoWindowReduceInvokable, CoGroupedBatchReduceInvokable, CoGroupedWindowReduceInvokable
[streaming] Reduce and GroupReduce invokable refactor and performance tweak