Custom class loaders

[mateuszjarzyna]

Hi, I've created method to use own, custom class loader. This change can resolve https://github.com/MatteoJoliveau/PlugFace/issues/19 by creating new class loader

`@RequiredArgsConstructor public class PluginClassLoaderCreator implements ClassLoaderCreator {

private final ClassLoader parentClassLoader;

@Override
public ClassLoader createClassLoader(URL[] jars) {
    return new URLClassLoader(jars, parentClassLoader);
}

}`

new PluginClassLoaderCreator(this.getClass().getClassLoader());

This code of course can break all security feature, but programmes should known the consequentness of passing no-default class loader.

[Col-E]

Could this also resolve the casting error from #24 ? I know loaders can do funny things with something that would normally seem trivial like casting.