Feature request: Add mean img chan2 and mean img chan2 corr as viewing modes in Manual Labeling

[marysethomas]

Currently in the Manual Labeling window we can switch between the following views: mean img, mean img (enhanced), correlation map, and max projection.

Would it be possible to add mean img chan2 and mean img chan2 corr as additional options?

Thank you!
-Maryse

[marysethomas]

Made a pull request here: #785