Add initial classes and traits for data sources.

This checkin also moves FilterGeometry to its own file.
Merging initial implementation of raster sources.
RasterBuilders now use RasterDefinition and ops.
Remove setDataDefinition from SourceBuilder.

Also, separate some classes into separate files; add some tests that
should have been checked in.
Integrate RasterDefinitions into builders.
RasterLayer now includes tile information.
Implement LocalRasterSource and DistributedRasterSource.
Initial support for execution of DataSources.

Debugging statements are still included.
Tests updated for current status.
Add LoadRasterSource and LoadTile operations.
Update tests to check result values.
Remove debug statements.
Update Add and Subtract for new API.

Add and Subtract no longer use the basic logic raster operations --
appropriate handling of tiles is done through the RasterSource.localAdd()
operation.
Initial implementation of sequence data sources.
Add eclipse related entries to .gitignore.
Add DistributedSeqSource test.
Add partition/chunk type to DataSource.
Change license from GPL 3 to Apache 2.

This commit also updates version numbers and does a bit of cleanup in README.md.
Take a stab at adding Mean
Added Mean to zonal.summary ops