is_backend & is_frontend

think we should have 2 function more relevant to the name of is_admin
might just be needing one function but one more dose not harm…

like it says in the comments:
* Does not inform on whether the user is an admin! Use capability checks to
* tell if the user should be accessing a section or not.

Its confusing! i thougth it checked for capability at first point. but find out its relative to the backend/frontend

function is_backend(){
  return is_admin();
}

function is_frontend(){
  return (!is_admin());
}