Add highlighting / custom formatting of data grid

[ryanhamilton]

Users would like to highlight cells:

• ,<,= number

• containing or equal to text
• show databars - e.g. Order book bid/ask column
• color scale - from green positive to red negative
• Icons - up/down arrow to show recent trend

Some of these are achieveable currently with either formatters (databar) OR per table row formatting. But these generic cases should be easily performable from the UI.

[ryanhamilton]

Keeping open as:

• Tables are most popular UI
• Closely related to #61

[ryanhamilton]

user-kf -user-sit would like "is it possible to dynamically color a numeric in a grid output? "