This also adjusts the method for comparing filters, allowing a chart to
define a "filterCompare" method that will be used to compare filters if
available.
This finally removes the date chart special case for setting filters.

Array instance checking will now use foo instanceof Array instead of
typeof(foo) == "array", which was unreliable (sometimes it's "object").

Trellis chart brush containers will now redraw the brush when set
externally.

renderBrush no longer takes brushG as a parameter. I'm not sure what I
was thinking when I made it so.

The deselected area will not yet fade.

The trellis chart still requires substantial refactoring and consistency
fixes; I'm not sure that the parameter specifications are currently
correct.