text: Title: dcc.Link: Use `href` as `children` if no children are defined
  Body: With HTML anchors, users are forced to provide a displayed content for the anchor, which can be as simple as the href itself..
  
  ```
  <a href='myurl'>myurl</a>
  ```
  
  1:1 correspondance in dcc.Link forces users to do the same thing:
  ```
  dcc.Link(
    href='myurl',
    children=['myurl']
  )
  ```
  
  Defaulting to href for inner content if no children is defined provides a default behavior that will be acceptable in certain situations and will simplify usage.