Show Summed Projections in Axis Alignment Widget

[Hovden]

Implement a checkbox to the right of "projection no" so that when it is checked the sum of all projections is displayed instead of one specific particular from the tiltseries.

"I find it easier to do this alignment if you show the sum of all projections rather than a single projection. The average shows a blur that is perpendicular to the tilt axis." - Peter