**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.

var props = {testProp: value};
  var propName = 'testProp' + Math.random().toString();
  var componentName = 'testComponent' + Math.random().toString();
  for (var i = 0; i < 3; i ++) {
    declaration(
      props,
      propName,
      componentName,
      'prop'
    );
  }
  expect(console.error.calls.count()).toBe(1);
  expect(console.error.calls.argsFor(0)[0]).toContain(
    'You are manually calling a React.PropTypes validation '
  );
  console.error.calls.reset();
}
describe('ReactPropTypes', function() {
  beforeEach(function() {
    PropTypes = require('ReactPropTypes');
    React = require('React');
    ReactFragment = require('ReactFragment');
    ReactPropTypeLocations = require('ReactPropTypeLocations');
    ReactTestUtils = require('ReactTestUtils');
    ReactPropTypesSecret = require('ReactPropTypesSecret');
  });
  describe('Primitive Types', function() {
    it('should warn for invalid strings', function() {
      typeCheckFail(
        PropTypes.string,