Allow widgets to be appended to LineGraphs as long as they implement draw, redraw and setScale.

Implemented setScale for LabelGroup
Implemented a tiny test of this functionality in lineGraphTests.html, which I am hoping Leslie will clean up.
Merge pull request #12 from mlippert/widget-refactor

Allow widgets to be appended to LineGraph - thanks Mike
fixed key check, more fields on NeffPop
fix to apply transforms to update selection as well as enter.
formatting on slider and numeric readout values