The old functionality where classes were directly copied to the
container can be done by setting `dropdownCssClass: ':all:'` when
initializing Select2.
This closes https://github.com/select2/select2/issues/2879.
This finally fixes and adds some integration tests to make sure
that `select2('data')` works as we are expecting. This also adds
tests for `select2('val')` and fixes undefined variable issues
that were spotted because of these tests.
We also no longer date stamp distribution builds.
This closes https://github.com/select2/select2/issues/3104.