Feature request: Add support for hooks

[nahall]

Add support for hooks, similar to how tea4cups does it. It would be nice if there was a kind of generic system, like tea4cups, where we could write scripts to execute before or after the job is processed, so that lprint doesn't really need much code to handle specific use cases, but with generic hook functionality we could just write scripts to handle the specific cases with short scripts. We personally just use posthooks in tea4cups currently but tea4cups also supports prehooks and I imagine some users would have need of those.

[michaelrsweet]

Moving this to PAPPL for potential future incorporation.

[michaelrsweet]

OK, so I have another printer application project I'm working on that will probably be more suitable than putting this functionality into PAPPL itself. Plus most of the containers that run the printer applications won't be setup to allow for running third-party executables outside of the container. Closing this bug for PAPPL, but keep an eye on OpenPrinting's main web site for future announcements...