bake: Make pipeline processing multi-process. Not many changes here, as it's pretty straightforward, but an API change for processors so they know if they're being initialized/disposed from the main process or from one of the workers. This makes it possible to do global stuff that has side-effects (e.g. create a directory) vs. doing in-memory stuff.

#!/bin/sh

CHEF_DIR=`dirname $0`
if `hash readlink 2>&-`; then
    LINKED_EXE=`readlink $0`
    if [ -n "$LINKED_EXE" ]; then
        CHEF_DIR=`dirname $LINKED_EXE`
    fi
fi
python $CHEF_DIR/../chef.py $@