Allow to register "global" param providers

[lolautruche]

Global param providers would be called for all views, so that it won't be necessary to configure them for each and every views.

[flovntp]

Allow to use ParamProviders for twig_globals (like this, even if it's a custom route from SF, paramProvider would be useable)

[lolautruche]

@flovntp For twig_globals it will be difficult since param providers are bound to ContentView, and it won't work for regular symfony controllers.

[andrerom]

So this will inject variables for all content views then, kind of like a default set of params each and every override rule can overload? Will it be siteaccess aware?

[lolautruche]

@andrerom Yes, that's the idea. Not sure of the point making the providers themselves siteaccess aware, but parameters passed to them could be.