Rename namespace class to {package.name}Package

Conflicts:

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

compiler/testData/writeSignature/MutableMapEntry.kt

@@ -1,6 +1,6 @@
 fun getEntry(): jet.MutableMap.MutableEntry<Int, String>? = null
 
-// method: namespace::getEntry
+// method: _DefaultPackage::getEntry
 // jvm signature:     ()Ljava/util/Map$Entry;
 // generic signature: ()Ljava/util/Map$Entry<Ljava/lang/Integer;Ljava/lang/String;>;
 // kotlin signature:  ()?Ljet/MutableMap.MutableEntry<Ljava/lang/Integer;Ljava/lang/String;>;