tests: When opening a file to check an exported result, close the file before exit.
BlockwiseFileset: Not tested (and therefore not supported) on Windows and Darwin.
tests: skip RESTfulBlockwiseFileset tests on mac and windows.
submodules: Updated dvidclient
tests: More cleanup of data checking operators before exit.
OpTrainRandomForestBlocked: If there aren't enough labels to train with, return None.
OpSlicedBlockedArrayCache: Don't mark everything dirty if the blockshape is dirty.  That's an error anyway.
OpFeatureMatrixCache: When handling dirty feature rois, only mark those blocks dirty that are already in the cache.
roi utilities: determineBlockShape(): Round when converting each dim to an int (results in more intuitive block shapes)
roi.py: Fixed doctests, minor cleanups.
OpBlockedSparseLabelArray: Don't set the entire image dirty when a label is deleted.  Mark each block with a separate dirty notification.
OpFeatureMatrixCache: Blocks with no labels are not dirty once they've been read.
tests: Fixed typo in assertion message.
OpCompressedCache: Ensure that chunkshape is always smaller than the blockshape, even for edge blocks (which are smaller than the other blocks).
Added OpCompressedUserLabelArray as a drop-in replacement for OpBlockedSparseLabelArray (except for some outputs) and test (based on a modified version of the OpBlockedSparseLabelArray test)
OpFeatureMatrixCache: If there are no labels and therefore no features, return a 0-length matrix with the correct number of columns.
Merge branch 'compressed-user-labels'
OpDenseLabelArray: Allow MetaInput to have multiple channels, and force output shape to have 1 channel.
tests: Dvid tests fixed to actually run on windows instead of just skipping them.