Rename namespace class to {package.name}Package

Conflicts:

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

compiler/testData/writeSignature/declarationSiteVariance/OutInOutPosition.kt

@@ -1,6 +1,6 @@
 fun f(): List<String> = throw Exception()
 
-// method: namespace::f
+// method: _DefaultPackage::f
 // jvm signature:     ()Ljava/util/List;
 // generic signature: ()Ljava/util/List<Ljava/lang/String;>;
 // kotlin signature:  ()Ljet/List<Ljava/lang/String;>;