Bug: Default size in Chart Workshop

The initial chart displayed by the Chart Workshop was $800\times 600$ pixels but the default selection for the ``Chart size'' item was $640\times 480$, so if you just pressed the ``Update'' button without changing any of the selections, the chart displayed would shrink. Even more jarring, in a $800\times 600$ chart with the default interval of one quarter, daily weights can be plotted as floats and sinkers, but at $640\times 480$ they don't fit, so the grey line format is used. I changed the initial selection to $800\times 600$ to agree with the default on initial display of the page.