AdvAgg 8.x-2.x Port

Luckily advagg core is not required to get some of the submodules working. Most AdvAgg sub components should be fairly easy to implement from my understanding like js minification; They should be able to stand on their own. For the 8.x branch of AdvAgg there are a couple of things I would like to change, the biggest one is changing the name of the advagg_js_compress module to advagg_js_minify; compression and minification are 2 different things, want to make this less confusing. Same for the advagg_css_compress and advagg_ext_compress modules.

The css/js cdn sub modules should be very low on the priority list; make them a single module and provide a way for it to go both ways; file to external, external to file.

The Async Font Loader should be easy to do as well and shouldn't require too many changes.

The validator stands on its own currently so porting should be easy to do.

Some parts of the modifier will be easy to implement, other parts of it requires deep integration with advagg core.

The bundler will be hard to do as well as advagg's core functionality. I'd like to have separate settings hash for css and js; currently they are combined. I do like the 3 hashes in the filename so that will stay.