Curation config / channel selection persistence

Currently, when a user selects a channel to use during curation, that channel selection is not persisted in any way when they start training. Instead, they have to remember and re-select it. Since we have decided to support multi-channel segmentations, the same will be true for seg1 and seg2 channels. We should develop a way to auto-populate the channel selections in training based on the user's selections in curation.