-Fixes issues with colors not parsing correctly. Saving an SvgDocument
resulted in RGB color values being converted to well known color names.

-Compile regex statements to improve performance.

-Make rendering a document threadsafe.

- Implemented .Net 3.5 support mostly by removing ISvgEventCaller
functionality in .Net 3.5 build
- Added ability to parse orient="auto"
- Added ability to parse colors such as rgb(#%, #%, #%)
- Fixed marker rendering implementation

- exponent support in units (IE sucks!)
- inherit font-size and font-family from root element on text elements
- allow empty text elements if there is a non empty TSPan

- Adding initial support for Write functionality. Units & Transforms mostly. Enums still need work. Needs support for an IsDirty concept so that that every possible attribute isn't written.