datepicker bootstrap

remove old jquery datepicker and replace it with a bootstrap one.

Notes:
- Had to add custom modification to the library to support the weeks number.
- The bootstrap datetimepicker library need moment.js in order to work
If I understand correctly, the `dp.show` event registered in the `events` manifest here before has been added in order to setup the default value when opening the datetimepicker. If true, this is not the right place to do it.
Why not managing this in a click event bound to `oe_datepicker_trigger` as it was the case before ?