TAJO-1008: Protocol buffer De/Serialization for EvalNode.
TAJO-1013: a complex equality condition including columns of the same table is recognized as a join condition.

Closes #123
Revert "TAJO-1008: Protocol buffer De/Serialization for EvalNode."

This reverts commit 49d52553c5e4ef37a6af4605befbe36b0dd36c3c.
TAJO-1008: Protocol buffer De/Serialization for EvalNode.