add items for Property sub-classes and validation options, see phetsi…

…ms/coulombs-law#63

checklists/code_review_checklist.md

@@ -344,6 +344,10 @@ var thoughts = happy ? ‘I am happy’ : ‘I am not happy :(’;
 
 - [ ] Naming for Property values:  All `AXON/Property` instances should be declared with the suffix `Property`.  For example, if a visible property is added, it should have the name `visibleProperty` instead of simply `visible`.  This will help to avoid confusion with non-Property definitions.
 
+- [ ] Properties should use type-specific subclasses where appropriate (.e.g BooleanProperty, NumberProperty, StringProperty) or provide documentation as to why they are not.
+
+- [ ] Are Property value validation options (`valueType`, `validValues`, etc...) utilized? Is their presence or lack thereof properly documented?
+
 - [ ] Line comments should generally be preceded by a blank line.  For example:
 
 ```js