Feature/didrocks

I would love to hear your thoughts about this branch. It returns (True, False) when mark_{install,upgrade,delete} is called. Technically a API break, but I doubt that anything used the return value of mark_install so far (but we could move it into experimental first or release it as part of a new 1.1 series or add a compat flag, I'm open for ideas :)

It also improves some doc strings. This is based on user feedback.