Android Extensions: Support LayoutContainer in code generation

plugins/android-extensions/android-extensions-compiler/testData/codegen/android/androidEntity/0.kt

@@ -0,0 +1,36 @@
+package test
+
+import android.app.Activity
+import android.view.View
+import android.widget.*
+import kotlinx.android.synthetic.main.layout.*
+import kotlinx.android.extensions.*
+
+class R {
+    class id {
+        companion object {
+            const val login = 5
+        }
+    }
+}
+
+class MyEntity(override val containerView: View) : LayoutContainer
+
+class MyActivity(): Activity() {
+    val loginItem = Button(this)
+
+    val entity = MyEntity(object : FrameLayout(this) {
+        override fun findViewById(id: Int) : View? = when(id) {
+            R.id.login -> loginItem
+            else -> null
+        }
+    })
+
+    public fun box(): String {
+        return if (entity.login.toString() == "Button") "OK" else ""
+    }
+}
+
+fun box(): String {
+    return MyActivity().box()
+}