Input TV should show the relative path, not the full path

[joeke]

When working with for example a CDN mediasource, which has a baseUrl or url set to the external CDN url, that url is also shown in the ImageCropper input TV. It should however show the relative path, and only use the url from the mediasource for showing thumbnails etc. This would also mean that when outputting on frontend, the correct url should be used, the same as with outputting core modx image TVs (see the renderOutput and prepareOutput methods in modTemplateVar class).