Added RasterSource methods for +,-,*,/
Fixing subproject builds
Merged in upstream, fixed tests.
Merge pull request #596 from joshmarcus/topic/node_history

History now includes node identification information.
Merge pull request #594 from lossyrob/localOpMethods

Added RasterSource methods for +,-,*,/
Merge branch 'master' of github.com:geotrellis/geotrellis into topic/distribute_data_sources
Minor README fixes.
Shutdown server in dev/cluster demo.
Include system name in Literal History objects.