Feature request: Check if delocalization directory is valid before dispatching job

[julianhess]

Currently, Canine waits until it actually starts delocalization to check that the delocalization location is valid (e.g., does not already exist, is writable, etc.)

I think it would be better to have these checks happen before the job is dispatched, to avoid the possibility of having a long, expensive job run to completion only to fail at the very end because it couldn't be delocalized.