Repository management

We have a lot of repositories, which need managing, tracking and auditing, and a hell of a lot of dependencies, which need tracking too.

Lots of things need to be build, but the first seems to be actually listing the repositories, which is not actually easy for normal folk to do without org access.

I've been looking at [gitshelf](https://github.com/gitshelf/gitshelf) and [rosinstall](https://github.com/vcstools/rosinstall), and they both (and others) seem to have a good foundation. `rosinstall` clearly wins on the fact it is in apt and dnf repos, so very easy for most folk to get a hold of and use.

So I've started building a set of rosinstall files:

https://github.com/jayvdb/meta/tree/rosinstall/rosinstall