Add "index" toggle for .h5 frame view instead of projecting images as omega

[kenygren]

Can we have an option where after loading non-aggregated images in, we can toggle a button to view with integer index numbers instead of the calculated omega range? Some of the images we load in for viewing are not necessarily indexed on omega - and often when we are checking images on-the-fly the index is just as useful as the omega range.

[psavery]

We do allow this internally. If you open the images via "File"->"Open"->"Images", the omega info is not shown (only the index).

However, the Simple Image Series loader currently requires omega. We should add a checkbox to make it optional there.

[psavery]

@bnmajor Can we make omegas optional in the simple image series loader?