Rework build settings to allow raw "go" tool usage.

Moved cgo settings into a pkg-config file (storage/engine/engine.pc)
which is created from storage/engine/engine.pc.in. Change the cgo
settings to find rocksdb in the same location for both normal builds and
docker builds.

Various cleanups to the Makefile now that we no longer need to set CGO_*
env variables.

Delete the Vagrantfile. It's likely currently broken.
so random thought here but... now that we have bootstrap. Where I was hoping to go with this was, if we check in the generated go code for the protos and sqlparser, which should change infrequently, then the bare go too just starts to work for us (go build, go run etc.)