**Do you want to request a _feature_ or report a _bug_?**
Enhancement

**What is the current behavior?**
Element type checker is not as informative as the other ones.

**What is the expected behavior?**
It would be nice to provide the actual type of the prop passed similarly to other type checkers. I.e., instead of 

> Invalid prop `Prop` supplied to `Component`, expected a single ReactElement.

say

> Invalid prop `Prop` of type `type` supplied to `Component`, expected a single ReactElement.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
Seeing this on 15.2.1 but I think it's also applicable to previous versions.

I know the general intention is to move away from prop types, but if there isn't a specific reason for the current behavior I can look into making this more pretty.

typeCheckFail(
        PropTypes.string,
        new Date(),
        'Invalid prop `testProp` of type `date` supplied to ' +
        '`testComponent`, expected `string`.'
      );
      typeCheckFail(
        PropTypes.string,
        /please/,
        'Invalid prop `testProp` of type `regexp` supplied to ' +
        '`testComponent`, expected `string`.'
      );
    });
    it('should not warn for valid values', function() {
      typeCheckPass(PropTypes.array, []);
      typeCheckPass(PropTypes.bool, false);
      typeCheckPass(PropTypes.func, function() {});
      typeCheckPass(PropTypes.number, 0);
      typeCheckPass(PropTypes.string, '');
      typeCheckPass(PropTypes.object, {});
      typeCheckPass(PropTypes.object, new Date());
      typeCheckPass(PropTypes.object, /please/);
      typeCheckPass(PropTypes.symbol, Symbol());
    });
    it('should be implicitly optional and not warn without values', function() {
      typeCheckPass(PropTypes.string, null);
      typeCheckPass(PropTypes.string, undefined);
    });
    it('should warn for missing required values', function() {
      typeCheckFail(PropTypes.string.isRequired, null, requiredMessage);