Form submission should save number fields as numbers in JSON

In order for this event handler to work, `cost`'s type must be an integer.

``` python
if data.cost >= 500:
change_state('Awaiting CFO Approval')
```

Which means the form data grabber should recongise the `` and save it as a number. This is like the one time when JavaScript is easier :P I assume there's no way to enable loose typing in event handlers, @mjumbewu, but worth asking..

Start by locating the form data grabber and the handling for . Verify that submitted numeric values are stored as numbers in JSON and that the shown Python comparison with data.cost works as intended.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.