chore($http): remove deprecated responseInterceptors functionality

Code cleanup! response interceptors have been deprecated for some time, and it is confusing to have
two APIs, one of which is slightly "hidden" and hard to see, which perform the same task. The newer
API is a bit cleaner and more visible, so this is naturally preferred.

BREAKING CHANGE:

Previously, it was possible to register a response interceptor like so:

    // register the interceptor as a service
    $provide.factory('myHttpInterceptor', function($q, dependency1, dependency2) {
      return function(promise) {
        return promise.then(function(response) {
          // do something on success
          return response;
        }, function(response) {
          // do something on error
          if (canRecover(response)) {
            return responseOrNewPromise
          }
          return $q.reject(response);
        });
      }
    });

    $httpProvider.responseInterceptors.push('myHttpInterceptor');

Now, one must use the newer API introduced in v1.1.4 (4ae46814), like so:

    $provide.factory('myHttpInterceptor', function($q) {
      return {
        response: function(response) {
          // do something on success
          return response;
        },
        responseError: function(response) {
          // do something on error
          if (canRecover(response)) {
            return responseOrNewPromise
          }
          return $q.reject(response);
        }
      };
    });

    $httpProvider.interceptors.push('myHttpInterceptor');

More details on the new interceptors API (which has been around as of v1.1.4) can be found at
https://docs.angularjs.org/api/ng/service/$http#interceptors

Closes #7266
Closes #7267
chore(package.json): add qq

e0375a61d03b489901b16d375b98a7f65db94af2 removed qq, but the changelog script still needs it
docs($anchorScroll): minor copyedit.

Singular-tense verb. Definite article.

Closes #7319
fix($httpBackend): Add missing expectHEAD() method

This was documented but not implemented.

With accompanying unit test to ensure the $httpBackend.expect*() methods exist.

Closes #7320