Create ability to capture timestamps for start and end of filling forms

In order to support the need for collecting audit information within forms in mUzima, there's need to create the ability to capture timestamps for:

• When a form is opened initially to fill data. Once this timestamp is captured, it should not be changed upon the subsequent reopening of the form.
• When a form is saved as complete. This timestamp should be updated in cases where the form is sent back to draft and then saved as complete.

The proposed approach is to introduce classes that can be attached to input fields within forms, such that the app automatically populates these fields if present.