New operation status for partial completion

[jnation3406]

For certain operations like median, It would be nice to attempt and produce a result before running out of memory, rather than just letting the operation run out of memory and failing or hanging. We could either add a new status option for partial completion, or just fill in the error message and COMPLETE status to show that it completed with some caveats.

• For Median and Stack operations, load in the images one by one and keep track of their size - when it has exceeded some safe limit we set, stop loading images and process what we have currently loaded
• Once complete, record some note in the "message" cache for the operation detailing what happened ("15/20 images used - memory limit reached") and set the operation to completed with that message and output
• Change frontend to check for the message and if its complete with a message, maybe change the button color or add a "!" icon or something to it to note it had an issue, and show the message on hover-over like we do with FAILED operations.

[LTDakin]

I remember a while back you allowed for partial outputs, did this satisfy this issue or is this a separate thing?

[jnation3406]

That was a separate thing (#74) - to allow an ongoing operation to report back its progress midway before it completes.

This issue is to support partially completing an operation if it has so many inputs that it would run out of memory, or otherwise fail partway through due to some issue with a single file within it. Like for instance if you want a median of 20 images, and 1/20 fails to load or is the wrong dimensions or something, then you could return a median with 19/20 of the input images + an associated error message rather than just failing completely. I don't know how much this is desired though.