Many improvements to the enhanced path shape.

The shape has now a concept of a viewbox with the original coordinate system and coordinates defined with the enhanced path parameters. The evaluating of parameters and formulae works with that to calculate the values used for creating the shape.

Those values get mapped into the shapes coordinate system and are then used for creating the outline.

This fixes the bounding box problems experienced with shapes changing its size when edited.

Implemented more commands and a circular-arc shape copied verbatim from oo2 to test these commands.

Splitted the template definitions into different functions inside the shape factory and use more complex structures as properties of the templates.