Bug737815 - Graphs Cannot Be Generated Correctly

Fix in html-barchart.scm, change loop condition
Bug 737815 - Graphs cannot be generated correctly

Revert x axis renderer from DateAxis to CategoryAxis.
It looks like the DateAxis renderer wasn't meant to be
used for a bar chart.
Redo the highlighter in barcharts.

The formatting code was removed with the introduction
of the zoom cursor. It continued to display
poorly formatted information though which is now fixed again
Some minor cosmetics in the barchart code