Add CacheBustingWorker support v2

[sandermarechal]

This is an updated version of #119, rebased on master and updated with regards to the changes in the CacheBustingWorker in assetic.

[stof]

Can you also update the XSD with the new config to support XML configs ?

[cordoval]

wonder if all this big tree can be wrapped each block into a method to refactor nicely the sections like elsewhere is done as this is getting too long

[sandermarechal]

Perhaps better in a separate PR?

[kingcrunch]

@sandermarechal 👍 Finish one task, than the next one.

[sandermarechal]

@stof I have updated the XSD

[Ninir]

This is amazing, thanks @sandermarechal @stof
Fixing a lot of issues and dev dependencies ;)

[sandermarechal]

@Ninir You're welcome. I will let someone else pick the fight over enabling this by default in a next major release of Symfony. There seemed to be some support for that in #119

[nurikabe]

I second @Ninir. Thank you very much for this.

[stof]

@sandermarechal No, #119 was not enabling by default.

[sandermarechal]

@stof I know, that's why this one isn't either. But there were quite some people giving you a +1 for enabling it by default. That's what I meant.