Worker: break out to a seperate subproject.

Keeping workers and lot of perferical stuff embedded in the code
base, it's much harder to port and change stuff. To be able to
rewrite it to handle multiple configurations at the same time, lot of
stuff needs to be rewritten. That means, it's much easier to keep the
codebase splitted up.

Signed-off-by: Max Sikstrom <msikstrom@op5.com>