title: Bootstrap: How to add dropdown.less?
body: <p>I need to add a calendar into a form.
  I want to install this project:
  <a href="https://github.com/vitalets/bootstrap-datepicker" rel="noreferrer">https://github.com/vitalets/bootstrap-datepicker</a></p>
  
  <p>But it is said that:
  Requires bootstrap’s dropdown component (dropdowns.less) for some styles, and bootstrap’s sprites (sprites.less and associated images) for arrows.</p>
  
  <p>How can i add that files to my app?</p>
  
  <p>Thank you very much!</p>