Projector2d Improvements

See: https://github.com/imglib/imglib/pull/23

This branch improves the performance of Projector2D by (a) Introduction RandomAccessibleProjector2D and IterableIntervalProjector2D and (b) code-tweaking in IterableIntervalProjector2D.

@tpietzsch I removed the old projectors again, fixed the resulting compilation errors (benchmark) and updated the javadoc. Anything I missed?