Updated Jackson/Joda/Spring date serialization configuration.

Using `JodaModule` from jackson-datatype-joda
(https://github.com/FasterXML/jackson-datatype-joda).
Changed DAO to use Objects.toStringHelper and Joda date/time.

java.util.Date == BAD
toStringHelper == EssentialGuava
In Progress: Create sheet editing ability.

RESTfulizing `TimeSheet` MVC resources.