Improve documentation of Reflection.type() for classloader issues

[clementdenis]

I've been replacing calls to the java.util.reflect package with equivalent code from fest-reflect, and I had an issue with type("...").load(), which throws a ClassNotFoundException when Class.forName("...") did not.

I thought that type("...").load() was strictly equivalent to Class.forName("..."), minus the checked exceptions. In fact, it is not : Class.forName() uses ClassLoader.getCallerClassLoader to determine the class loader to use, while fest-reflect's Type.load() uses the classloader used to load itself.

In complex cases (maven + ant in my case), fest-reflect's jar is not loaded in the same class loader as the application classes, which causes the problem (and can be fixed with .withClassLoader(getClass().getClassLoader()) in the calling class).

A solution would be to use sun.reflect.Reflection.getCallerClass() to determine the right classloader, but it would add a dependency to a sun package (bad bad bad).

When JEP 176 is available, it should be possible to use this new mechanism to implement a reliable detection of the caller class loader.

In the meantime, the documentation should explicitly mention this classloading issue, as it can be tricky to debug.