Compressing a folder that is already in the watchlist should pre-tick and disable the "Add to Watcher" checkbox

[Iridium-IO]

another suggestion: as a further improvement, when a folder is added to the queue from the watched folders list, it shouldn’t be necessary to check the 'Watch folder for changes' option again, since the folder is already being monitored. Shouldn’t this option appear ticked but greyed out unless the folder is removed from the watch list?

Originally posted by @Starbuck1991 in #519