Rename the module

[mscherer]

As there is some community who may want to build more than middleman, it might make sense to rename the module to be static_builder rather than middleman_builder.

So we need to have a list of downstream user we know and be prepared to switch.

[duck-rh]

Here I have: Community / oVirt / RDO / OSCI / Gluster
(MI no more uses it)
Anything else?

[mscherer]

Nope. I think we can just rename and fix. The failure would either be quite visible anyway, or wouldn't break anything but deployment of infra, so no userfacing breakage.

[duck-rh]

Done, let's fix now.

[duck-rh]

It would be nice to change the default builder_username too, but this means renaming things on the deployed machines too.

[duck-rh]

I fixed all of them except Gluster because I don't have access so I made a PR.

[duck-rh]

Updated the doc slightly in #18

[mscherer]

We can just add a alias on the variable for builder_username.