Created module idea-test-framework and moved classes needed for idea tests there

Moved tests for completion and their test data into module idea-completion

idea/idea-completion/testData/smart/constructor/Nullable.kt

@@ -0,0 +1,7 @@
+class Foo
+
+fun foo(p : Any){
+    var a : Foo? = <caret>
+}
+
+// EXIST: { lookupString:"Foo", itemText:"Foo", tailText: "() (<root>)" }