JS backend: remove RegressionMergeEcmaTest
JS backend: fix inheritance from native class & remove createConstructor() function from stdLib
JS backend: fix class object access A.object$() -> A.object
JS backend: drop Kotlin.keys
JS backend: fix is for trait. #KT-3519 fixed
JS backend: refactoring: extract CallArgumentTranslator from AbstractCallExpressionTranslator and CallExpressionTranslator