projector::map() called too often

Create a new 8 slice hyperstack (1 c, 1 t). Run Stack To Images. If you put a print statement in `CompositeXYProjector.map()` you'll see it is called dozens of times.

Migrated-From: http://trac.imagej.net/ticket/1159

Reproduce the issue with an 8-slice hyperstack using Stack To Images, then inspect CompositeXYProjector.map(), the entry point named in the report. Trace why it is called dozens of times and define completion as avoiding unnecessary calls while preserving the Stack To Images result.

Written by the indexing model from the issue text.