(wip) Layer Cache

awesomeness of caching layers in dockerfiles!
might need to brush up on my awk but doest this line only replace one instance of # runnable-cache, i thought we wanted to as many of these ass possible?

also I am pretty sure product is going to want to change `runnable-cache` we should make is an ENV at the top of the file.  (remember if you this you have to pass env's into awk BEGIN{a='$one';b='$two'})