Initial implementation of the ISO week datepicker extension.

Extended the bootstrap-datetimepicker plugin. 

- The week-start option was already provided in the plugin so we ca just use that to make Monday the first day.
- Added an option to show or hide the weeks column.
- Extended the plugin to parse and display the `YYYY`, `ww` and `d` tokens in the ISO week date format.
- Added a sample under `examples/` directory.

Notes:

- Bootstrap, both the submodule and the Bower dependency, could compile an empty CSS. Possibly caused by [this issue](https://github.com/twitter/bootstrap/issues/8088). As a quick patch, what I did was download the compiled versions on Bootstrap's page and copied them to where the compiled versions would be placed. [A temporary fix](https://github.com/twitter/bootstrap/issues/8088#issuecomment-20168930) is also stated at the bottom.