Helper functions for memory management with J2V8

V8Extensions.kt

/**
 * This executes the supplied lambda in the scope of a J2V8 MemoryManager, ensuring that all 
 * V8Object instances allocated in the scope are cleaned up on exit.
 */
inline fun <T> V8.scope(body: () -> T) : T {
    val scope = MemoryManager(this)
    try {
        return body()
    } finally {
        scope.release()
    }
}