Do not report NO_CLASS_OBJECT when namespacesAllowed=true

Now with nested classes the expression "A.something" makes sense even when A
doesn't have a class object ("something" could be a nested class)

Also "A" expression now gets a NamespaceType with the scope of all static
nested classes of A

 #KT-1174 In Progress

compiler/testData/diagnostics/tests/ClassObjects.kt

@@ -21,7 +21,7 @@ object b {
 }
 
 val a = A.x
-val c = <!NO_CLASS_OBJECT!>B<!>.x
+val c = B.<!UNRESOLVED_REFERENCE!>x<!>
 val d = b.<!UNRESOLVED_REFERENCE!>x<!>
 
 val s = <!NO_CLASS_OBJECT!>System<!>  // error