Add FILE_FLAG_REPLACE

This will be used to replace existing files by unlinking them before
opening them.
Create directory part of stdout/err redirection files
Rename some cron related types
Add process monitor to delay program scheduler start in full image

If the program has DISPLAY set then wait until lxpanel started or a
timeout occurred.
Complain if the cron subsystem is shutdown while there are still entries added to it
Strip trailing whitesapce from image version
Reduce severity level of some common file warnings to debug