Several fixes for issues with bar and pie chart

[SteveBallantine]

Pie chart - old version re-ordered data into order by value. Didn't like this behaviour and it caused problems with the labels/colours so removed it. minPercent and maxSlices functionality modified in order to take account of this. VBarchart - labels fixed (they just didn't work before). Modified behaviour so that if a label overlaps a previous label then Raphel will draw the label lower rather than just removing it. G.Raphael - I was running into a problem where the popup would move up the page each time it appeared. I've fixed this for my case, not sure if it breaks other cases or not though..