Remove qtip

See https://github.com/sonata-project/SonataAdminBundle/pull/1397

@rande

> I will prefer to have one PR which remove non bootstrap stuff, like : qtip and modal. and another PR with solve the issue with jQuery

I must say: I don't know exactly, what you mean with "non-bootstrap stuff: modal". I mean, the only references I could found were part of bootstrap. Can you give me a hint?