Added Dimensionality concept into the type system.

Changed crosses to use the Dimensionality of a Geometry instead of overloading across specific instances.
Modified contains, crosses, and within to use Dimensions.
Merge pull request #743 from lossyrob/geometry/methods

Added Dimensionality concept into the type system.
fix bug in Histogram.getMean

also switched it to use delta-mean method to avoid possible overflows
Added unit test for Histogram.getMode
Merge pull request #744 from echeipesh/fix/statistics

Fix/statistics
Added .statistics() to RasterSource
Merge pull request #745 from echeipesh/fix/statistics

Added .statistics() to RasterSource