- Adding a descendants convenience methods (similar to the Xml to Linq
API)
- Removed non-functional property from the SvgDescription class to
encourage use of the Content property instead
- Added unit test project for unit test of new functionality.

- Fix issues with calculating the next coordinate after a close figure
and a relative move
- Allow the std. deviation in a gaussian blur to be a float.
- Allow "none" for a unit collection
- Allow a marker to scale with either the stroke width or the use a
custom coordinate space
- Allow gradients to reference other gradients defined later in the SVG
- Respect the font and fill styles of TextSpan elements.  Current
support is still partial.
- Fix href attribute bug on the SVG use element

- 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

Read EntityReference node and add it to the SvgDocument.

```
<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg" width="800px" height="800px">
  <g>
    <rect width="200px" height="200px" fill="black" />
    <text x="100px" y="100px" font-family="Verdana" font-size="24" fill="white" text-anchor="middle">&name;</text>
  </g>
</svg>
```

Moved Display="none" hack & Added .Render check for : if (!Visible ||
!Displayable)

Also, minor change to logic of SvgBoolConverter so bad visibility values
(other than "hidden" or "collapse") wouldn't accidentally hide element

- 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

Some programs (like InkScape) use single quotes for the font-family.
I've added the single quote character, to the trim.

Added support for dx and dy properties for text. A bit of plumbing was already in place so I completed that.
http://www.w3.org/TR/SVG11/text.html#TextElementDXAttribute
http://www.w3.org/TR/SVG11/text.html#TextElementDYAttribute

To get the Bounds, the Union method of the rectangle must be called only when the first rectangle has been set. If the Renctangle is empty, use the first children's Bound, as a rectangle.

http://www.w3.org/TR/SVG/pservers.html#RadialGradientElementFXAttribute