Fix 2331

This fixes the various issues reported under issue #2331.  Specifically it resolves the following issues and provides passing tests to cover each:

* initDate property when present on datepicker-options was not being handled correctly by the datepicker dropdown.
* init-date attribute worked when used on a datepicker but not a datepicker dropdown.  It now works the same on both.
* init-date attribute was only evaluated when the datepicker dropdown was initialized.  It is now watched and will impact the date displayed in the dropdown up until the point were a date is selected or the model is assigned a date programatically.

Please let me know if you have any questions, comments or concerns.