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.

from textile import textile
from piecrust.formatting.base import Formatter


class TextileFormatter(Formatter):
    FORMAT_NAMES = ['textile', 'text']
    OUTPUT_FORMAT = 'html'

    def render(self, format_name, text):
        assert format_name in self.FORMAT_NAMES
        return textile(text)