FIR: Introduce new classifier descriptors aka 'cones'

compiler/fir/resolve/src/org/jetbrains/kotlin/descriptors/AbstractFirBasedDescriptor.kt

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.descriptors
+
+import org.jetbrains.kotlin.fir.FirBasedDescriptor
+import org.jetbrains.kotlin.fir.FirDescriptorOwner
+import org.jetbrains.kotlin.fir.FirElement
+
+abstract class AbstractFirBasedDescriptor<E> : FirBasedDescriptor<E> where E : FirElement, E : FirDescriptorOwner<E> {
+
+    override lateinit var fir: E
+
+    override fun bind(e: E) {
+        fir = e
+    }
+}