Disable focus prevention by default
Tweak debug output and add simple log-macros

compLogMessage isn't used and isn't fine grained enough for people to debug.
compLog(), compWarn() and compDebug() are all trivial to use, and reasonably
self-explanatory.

The output might be somewhat intimidating to users, but this is mostly going
to end up in ~/.xsession-errors, and it's better to have useful messages
than no messages.

I'll be using this and gradually removing compLogMessage() over time.
Don't try to update pixmaps for invisible windows

Trying to get the geometry of invisible windows, or decorations, meant
getting tons of X errors. This slightly reduces this spam.

Fixes #25