Rename namespace class to {package.name}Package

Conflicts:

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

compiler/testData/writeSignature/IntQ.kt

@@ -1,6 +1,6 @@
 fun sometimes(): Int? = null
 
-// method: namespace::sometimes
+// method: _DefaultPackage::sometimes
 // jvm signature:     ()Ljava/lang/Integer;
 // generic signature: null
 // kotlin signature:  ()?Ljava/lang/Integer; // TODO: need to skip kotlin signature