Tab-completion for %opts and %%opts magic now occurs at cursor position
Docstring fix and other minor fixes for improved readability
Indexing into OptionsGroups improved for groups containing one OptionMap
Added labels property on Overlays and label parameter may now be set
Removed rgb property from SheetOverlay as this is a channel reduction
Added RGBA operation to transforms to replace SheetOverlay rgb property
Made the labels on returned SheetViews consistent across transforms
Added AlphaOverlay operation to transforms to view overlays with alpha
Introduced ChannelOpts and channels group to define channel reductions
SheetPlots now reduce Overlay channels according to channel definitions
Introduced %%channels magic to define the channels on a displayed view
Fixed bug and Pyflakes error in the Colorize ViewOperation