[Template] Added lowercaseName option

Can we merge this? here''s summary

Often controller actions named as ```viewSummaryAction()``` or ```viewSomething()```
but desired twig template names are ```view_summary.html.twig``` and ```view_something.html.twig``` but with current @Template it seems not possible to achieve this (except full template path like @Template(FooBarBundle:Controller:view_summary.html.twig))

so, ```@Template(lowercaseName=true)``` will do all work above, I think idea is clear.
Thanks