Iteration 1 of tspan functionality
Iteration 2 of tspan functionality

- Support more font styles
- Fix problems with parsing 'em' svg units introduced by trying to parse
2e-5 double formats
- Move font properties to SvgVisualElement class as grouping elements
can also contain them
- Properly inherit font properties via the parent list
- Properly handle tspan offsets
- Support for .Net 3.5
Iteration 3 of tspan functionality

- Begin allowing character positioning within a text element
- Start fixing bugs with linear gradients