Fix issues caused by mixed locales

TimesSquare currently relies heavily on the default locale. This causes the build to break on some platforms with a different default locale than the one the tests were written against because some assumptions do not hold anymore on these platforms. Another problem is that if `CalendarPickerView` is configured with a different than the default locale, multiple locales are at work at the same time. This causes some funny behaviour like german month/day names with weeks starting on Sunday instead of Monday.

This pull requests addresses these problems by ensuring that only one locale is used -- the one `CalendarPickerView` was originally configured with. This can either be the default locale or another locale that has now to be passed as third argument to the `init` method. I hat to move it there to keep the initialization logic sane.