Use react-datepicker instead of pickadate

Fixes the issue with datepickers on mobile not appearing. The current datepicker inserts its element on at the same level than the input that triggers it. This is an issue in several cases where the parent does not have enough height/width (because there is not content for example), which causes the datepicker to be either cropped or even not displayed.

This new datepicker inserts it at the document.body level, which is better. The translations are using those from moment.