Fixes and minor improvements to PlanarPlaneSubsetLocalizinhCursor
Fixes and minor improvements to PlanarPlaneSubsetCursor
Added asserts in PlanarImg

Added asserts to cursor( Interval ) and localizingCursor( Interval )
in PlanarImg.
Added AbstractSubIntervalIterableCursorTest

Provides basic tests for SubIntervalIterable Cursors.
Added PlanarIterableSubIntervalCursorTest
Added ArrayIterableSubIntervalCursorTest
Added IterableSubIntervalBenchmark

Benchmark for comparing performance of unoptimized vs optimized
cursors and localizingCursors.