Add custom config property(optional) for resolving relative links

[bavicj]

The plugin uses grails.serverURL to handle relative links. Can you add support for some custom config property which can override this behaviour?It would be useful when you want to easily specify different url base for resources.

For example, I have an application using SSL, so my grails.serverURL = 'https://....'.
When rendering engine want to resolve css and images, application also makes https request, but it does not have proper certificate (it's not the browser).
If I could specify some other config variable to 'http:localhost:8080' for example, than the application would not have to go via apache, and the resources will be fetched without any problems.

Thank you