add Fill operation to hydrology
add test for fill operation in hydrology
add Fill operation to hydrology
fixes
Merge remote-tracking branch 'upstream/master' into hydrology
fix Fill opertaion
fixing issues
Merge remote-tracking branch 'markko/hydrology'
Fixes to syntax and other things.
Merge remote-tracking branch 'upstream/master' into hydrology
Merge pull request #1 from lossyrob/fillop

Fillop
Merge branch 'hydrology' of https://github.com/Markko/geotrellis into hydrology
Added 8-neighbor connectivity to RegionGroup.

Fixes #527
Merge pull request #657 from lossyrob/regiongroup-vector-8

Added 8-neighbor connectivity to RegionGroup.
Simplified actor system by removing 'Dispatcher', and .dispatch and .remote Op methods.

These methods have been replaced by .distribute, which distributes the opeartion it is run on. The .dispatch operation was created so that all children operations of an operation would be run on the cluster router, because it used to be the case that the tile operations were wrapped in another operation (that would then have .dispatch called on it). This level of complexity isn't needed anymore with RasterSource and .distribute, so was removed.
Implemented filter on Operation
Addressed TODOs. Some are left pending other issues.
Merge remote-tracking branch 'upstream/master' into refactor-todos
Merge pull request #659 from lossyrob/refactor-todos

Simplify actor system by removing Dispatcher and .dispatch, .remote
Seperated out mutable histogram conecpt, made ConstantHistogram