[Entity] rename EqualableInterface to EquatableInterface #1
[Entity] rename EquatableInterface::equalTo() to equals() #1
[Entity] rename CopyableInterface::copyFrom() to copyTo() #1
[Entity] rename the namespace Entity\Behavior to Entity\Operation #1
[Entity] add OperationInterface #1
[Entity] change ComparableInterface, CopyableInterface, and EquatableInterface to extend OperationInterface #1
fix CS
add missing copyright year