New Tree/Table Editor: other data channels

[corranwebster]

Implement a way for models to provide colour (eg. colour mapped), image, checkbox, tooltip, etc. information that may be used by tables to display the data. Since the way to adapt raw data to these other channels is likely to be fairly standard across underlying data models, this should ideally be done in a way that can be composed into the model or on top of it.

Channels that have been added:

• Text
• Editor value
• Image
• Checkbox
• Tooltip
• Color