Tasks FFmpeg, MediaConch, MediaInfo are internally marked as optional

[pjotrek-b]

Currently, all tasks derived from class AbstractTaskExecFF are internally marked as "skipable".
This is probably not the case anymore, and should be removed so that missing config options cause a config error exception.

[pjotrek-b]

Got it wrong!
The "skipIt()" call in loadSettings() only means that the config variables don't HAVE TO exist for each (sub)folder of an Item.

The current code skips the task (without an ERROR!), if ONE of its settings is missing.

It would be better to go to error IF: FFmpeg Task is set in the Tasklist[], but has NO valid config block for any folder.
So the users knows that the Task will /never/ be called.

[pjotrek-b]

The question is though:
How to implement that?

Idea: Use CIItem::$memory for that?