Improve formatting functionality on grid

[Nathan Toone]

Would be nice if we could do some (or all) of the following:

Pass "_item" as the field - meaning that the entire item gets passed down to the formatter function.

Allow the formatter function to return a widget or a dojo.Deferred object instead of being limited to returning strings.

Allow the formatter fucntions to execute within the scope of another object or widget.

[Nathan Toone]

Patch and test case which implements this functionality

[Nathan Toone]

(In [17709]) Fixes #9373 improve grid formatting functionality and add test case !strict

[Nathan Toone]

(In [17720]) Refs #9373 update test case to clear cache when needed