Add Twig functions for cmf_document_path and cmf_document_url

[symfony-cmf]

Add Twig functions for cmf_document_path and cmf_document_url

[dbu]

i think route generation should always work outside the current domain context, and we need a separate generator for that, as discussed in symfony-cmf/symfony-cmf#182

i think it makes sense to have these functions, still go through the normal chain router when generating but catch all exceptions and log them on a configurable level. maybe you want to know even in prod so you can fix things occasionally. for dev, if you want to get fancy we can also (later) add a feature to the debug toolbar.

the support for uuid + path to make editing links more stable should just go into the cmf route generator and not be specific to these twig functions.

[dbu]

@benglass do you want to do a PR for those functions?

[dbu]

btw, this should be on RoutingBundle as here in the component we don't know about twig.

[benglass]

Moved to symfony-cmf/routing-bundle#239