[2.3] [WIP][FrameworkBundle] Add support for the '@Bundle/Path/template.format.engi...

...ne' notation

@fabpot what's your opinion on this change ? It would allow for more consistency.

Todo - id accepted:

- [ ] PR header
- [ ] UTs
- [ ] Document the BC break
- [ ] Pass a Bundle map to the parser (AcmeDemo => AcmeDemoBundle) to be consistent w/ Twig & faster - that's an other BC break
- [ ] fix #6919 (disable NS parsing by Twig, always use the Template Name Parser)