[Spark-1461] Deferred Expression Evaluation (short-circuit evaluation)

This patch unify the foldable & nullable interface for Expression. 
1) Deterministic-less UDF (like Rand()) can not be folded.
2) Short-circut will significantly improves the performance in Expression Evaluation, however, the stateful UDF should not be ignored in a short-circuit evaluation(e.g. in expression: col1 > 0 and row_sequence() < 1000, row_sequence() can not be ignored even if col1 > 0 is false)

I brought an concept of DeferredObject from Hive, which has 2 kinds of children classes (EagerResult / DeferredResult), the former requires triggering the evaluation before it's created, while the later trigger the evaluation when first called its get() method.