Datepicker update

- Updated Datepicker to v1.3.0
- Updated CSS (Added compiled file, the source is in LESS format)
- Updated HTML where the datepicker is used
- Fixed JS function in scripts.js which was interfering with the new datepicker
- Removed readonly markings (hope it's ok, I think it also looks cleaner now)
- Fixes #54: Calendar overlap issue
Oh no, that's not what I meant. :D
Simply place the bootstrap-datepicker.css into the sass folder and use `@import "bootstrap-datepicker.css"` directly after the Font Awesome import. This will ensure we can update the datepicker.css at any time but it will be included directly into the style.css