Adds toggling of Datasets via clicking on the colorchip in legend.

Adds a couple of minor changes to jquery.flot.js.  The first is the addition of a series.show value.  This lets us keep our data but show / hide it as necessary in a way that should work with any plugins that add graph types.

The second is an addition of some markup that allows us to sync up datasets to legend display.  This may break when showing sub-graph for zooming / selection because it is id based, not class based.

The remaining changes in this set is the actual plugin itself.