Adding asset compilation

Adding asset compilation. Although there is still question how to add option that would disable asset compilation, something like the marker disable_asset_compilation we use in the v2 cartridge, cause user can build the image with already precompiled assets, which he precompiled locally.
Wasn't sure how to disable the precompilation in a dockerish way, cause we would need to introduce some kind of convention, which we don't want, so now the compilation runs everytime(if it meets the conditions).
Any tip on that ?