make commtrack wrapper helpers convert values explicitly

NOTE: I'd like the eyes of @czue or @mrgriscom before merging this

Make `StockStatus` and `StockTransaction` subclass a new `FormDataSchema` that has a `force_wrap` function and disables the `wrap` function. `force_wrap` modifies the values passed in based on the property type, forcing them to the proper type if they're a string.

fixes: http://manage.dimagi.com/default.asp?73921