**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.

function validate(props, propName, componentName, location, propFullName) {
    if (!ReactElement.isValidElement(props[propName])) {
      var locationName = ReactPropTypeLocationNames[location];
      return new Error(
        `Invalid ${locationName} \`${propFullName}\` supplied to ` +
        `\`${componentName}\`, expected a single ReactElement.`
      );
    }
    return null;
  }
  return createChainableTypeChecker(validate);
}
function createInstanceTypeChecker(expectedClass) {
  function validate(props, propName, componentName, location, propFullName) {
    if (!(props[propName] instanceof expectedClass)) {
      var locationName = ReactPropTypeLocationNames[location];
      var expectedClassName = expectedClass.name || ANONYMOUS;
      var actualClassName = getClassName(props[propName]);
      return new Error(
        `Invalid ${locationName} \`${propFullName}\` of type ` +
        `\`${actualClassName}\` supplied to \`${componentName}\`, expected ` +
        `instance of \`${expectedClassName}\`.`
      );
    }
    return null;
  }
  return createChainableTypeChecker(validate);
}
function createEnumTypeChecker(expectedValues) {