Feature staffing shift component 3296

Sorry for the big commit.

Added a staffing shift component that can be used to select a start and end date.
Also added test cases for the above component.


A24group/Triage#3296

Plz review

Test
 * Check out
 * Run test cases
 * Compile jar
 * Copy jar over to triage
 * Run cap a24deploy:gwt:application_compile
 * Make sure everything run as expected.