1) Add Powerlanguage support for drawing rectangle, horizontal line and vertical line.
Rectangle should allow border, fill colour and fill transparency to be set by code.

2) Improve the draw type for Line, allowing the section above/below the line to be filled and transparency set.
Section above/below the line should be user defined as:
between the line and zero
between the line and another line
between the line and +/- infinity

3) Add support for chart background shading. This should include setting the fill colour and transparency. Each background section per bar on the chart should be configurable.