ENH: add identity(IntRange) and Istream operator for common types

- provides consistency with identity(label, label) and looks more
  familiar than using labelRange::labels()

- relocates labelRange IO operators to IntRange

ENH: make sliceRange interators random access

STYLE: scalarRanges::match() instead of predicate operator

applications/test/labelRanges/Test-labelRanges.C

@@ -70,6 +70,11 @@ int main(int argc, char *argv[])
         labelRange::debug = 1;
     }
 
+    {
+        labelRange range(5, 10);
+        Info<< "identity: " << identity(range) << nl;
+    }
+
     {
         Info<<"test sorting" << endl;
         DynamicList<labelRange> list1(10);