feat(calendar): remove data values on destroy

[lubber-de]

Description

data saved to the jquery calendar object was not removed on destroy. This leads to situations when a re-instantiation of the same calendar gets confused about different setting than the previous (data()-stored) values.

Testcase

• Open the calendar, it should show the 6th of April in the header

Broken

• It shows the first of April https://jsfiddle.net/978rct0k/7/

• It shows the 6th of April https://jsfiddle.net/lubber/b04zkxf6/

Closes

3031