Initial date picker view and template
Add help button and text and improve formatting
Allow the user to choose between or not between for date ranges
Fix getValue, setValue, and setOperator to support -range and empty value
Properly set the UI values based on the operator and value
Revert "Properly set the UI values based on the operator and value"

This reverts commit 52acc19d3111722ec99730d75049b31aed329012.
Set the context in onRender method of the date range control
Merge pull request #171 from cbmi/issue-134

Implement date picker functionality for datetime fields