shape directives

[seiyria]

• [ ] gradient (id, type [radial, linear] - support N colors, positions, sizes, directions)
• [x] rectangle (index, x, y, width, height, [color, innercolor | gradientId, thickness])
• [x] ellipse (index, x, y, width, height, [color, innercolor | gradientId, thickness])
• [ ] generic polygon
• [ ] pie (?)
• [ ] line

Important features right now are line and rectangle.

gradients will also need to be figured out - they should be as flexible as css gradients and support all of the features of them