use schema.org types for RDFa mappings

[dbu]

see symfony-cmf/symfony-cmf-website@454b2ef

and also document this in CreateBundle doc and createphp doc

[marekkalnik]

I'll take a look, but I'm not sure if I'll be capable of doing it fast (I haven't used this bundle yet), so if anyone else wants do have a go, don't hesitate.

[lsmith77]

great. essentially have a look at the available schema.org types. then adjust the rdfa mappings in the Resource directory accordingly.