Allow camel-freemarker template cache duration to be specified

The camel-freemarker component supports caching of template files; however, the cache period that is applied is always 5 seconds – which is the default cache delay defined in the FreeMarker Configuration. This short cache window seems incongruent with likely uses of FreeMarker within a Camel route. Camel should allow the template cache duration to be specified as part of the component's URI definition so that longer cache periods can be configured in a route.