Change name exoweb-foss -> exocontrib

[Bjørn Stabell]

I've changed the name of the group from exoweb-foss to exocontrib to
better fit the exocontrib site that we have up already.

This means the email changes from

exowe...@googlegroups.com
to exoco...@googlegroups.com

and the group URL changes from

https://groups.google.com/group/exoweb-foss/
to https://groups.google.com/group/exocontrib/

Rgds,
Bjorn