Remove use of commons code

Following the axiom "a little copying is better than a little dep" this version removes the use of the common code and instead embeds that code into each project.

It is hoped that it will now be possible to do GO111MODULE=on go get github.com/corsc/go-tools/fiximports@v1.2.3 (and similar for other tools)

Edit: This is still not possible 🤦