Completely rewritten keyword completion implementation using another approach

#KT-2816 Fixed

idea/testData/completion/keywords/PropertySetter.kt

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2010-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+class Some {
+    var a : Int
+        get() = 0
+        <caret>
+}
+
+// EXIST:  abstract
+// EXIST:  annotation
+// EXIST:  as
+// EXIST:  class
+// EXIST:  enum
+// EXIST:  final
+// EXIST:  fun
+// EXIST:  get
+/*TODO*/
+// EXIST:  in
+/*why?*/
+// EXIST:  inner
+// EXIST:  internal
+// EXIST:  object
+// EXIST:  open
+// EXIST:  out
+/*why?*/
+// EXIST:  override
+// EXIST:  private
+// EXIST:  protected
+// EXIST:  public
+// EXIST: set
+// EXIST:  trait
+// EXIST:  val
+// EXIST:  var
+// EXIST:  vararg
+/*why?*/
+// NUMBER: 23