Rename namespace class to {package.name}Package

Conflicts:

	compiler/jet.as.java.psi/src/org/jetbrains/jet/asJava/JavaElementFinder.java

compiler/testData/writeSignature/NothingQ.kt

@@ -1,6 +1,6 @@
 fun nothingq(): Nothing? = null
 
-// method: namespace::nothingq
+// method: _DefaultPackage::nothingq
 // jvm signature:     ()Ljava/lang/Object;
 // generic signature: null
 // kotlin signature:  ()?Ljet/Nothing;