Use AbstractTemplateViewResolverProperties as the base class for
GroovyTemplateProperties since the Spring GroovyMarkupViewResolver is
an AbstractTemplateViewResolver.

The auto-configuration for Groovy is now more aligned with the existing
Freemarker and Velocity auto-configuration, with a `resourceLoaderPath`
property being used instead of `prefix`.

Fixes gh-3365
Closes gh-3374