[Rock-dev] Updates to Logger

[Sylvain Joyeux]

> On another note: I would argue to not set any packages to stable right now.
> I don't see any advantage of leaving out all debug information, other than
> maybe size.
Running strip on a rock installation seriously reduces its size (I
don't have the numbers right now, will try to get them). That's a few
GB saved, which when multiplied by the number of people that have
their own personal install on a size-constrained SSD you can find in
robots, using stable is not such a bad proposition.

I was rather wondering whether we could not find a workflow that would
allow people (as opposed to package developers) to control what gets
compiled in a more fine-grained way at the autoproj level:
 - debug info
 - optimization level
 - base log level

A large majority of people do not want any debug info on any of the
rock.core packages.

Sylvain