Added majority operation
Update signature of Collect to take an Operation.

Collect is updated to take an operation that returns a sequence of ops, instead
of taking a sequence of ops directly.

CollectArray is deprecated in favor of using logic.Collect directly.
Update signature of Mean and Variety to take Seq[Raster].

Mean and Variety now take Seq[Raster] instead of Array[Raster], and no longer
use the depreciated CollectArray.
Created ColorMap operation.

Takes in a map of breaks to colors and options for how the values
should be mapped to the breaks, and returns a color raster.
Merge remote-tracking branch 'upstream/master' into localops/majorityminority
Added Minority operation
Merge pull request #536 from joshmarcus/topic/collect

Update signature of Collect to take an Operation.
Merge remote-tracking branch 'upstream/master' into localops/majorityminority
Updated for merge of upstream
Merge pull request #537 from lossyrob/op/colormap

Created ColorMap operation.
Added Combination operation
Merge pull request #538 from lossyrob/localops/majorityminority

Created Majority \ Minority operations
Merge pull request #539 from lossyrob/localops/combine

Added Combination operation
Removing placeholder file.