Still a little raw - have a look and let me know what you think

- Changes to get texts displaying bold / normal weight
- Changes to get textspans work correctly
- Made (semi-hardcoded) document metadata section - allow reading and regurgitating metdata tag from an original source document
- Included image
- Modified paths to allow for scientific notation
- Included ability to have markers for path ends (arrow ends etc)

* fixed missing files

* added few enum converters

* added precise MeasureString method

* added implicit operator from RectangleF to SvgViewBox

* SvgDocument can calculate its size in percentage
* SvgTransform collection can return all matrices multiplied

* added method to collect paths of children elements
* fixed possible bug getinheritedattribute

* fill can be null -> none in XML
* added type converters for enums
* added type converter for unitcollection
* fixes several viewbox bugs
* document can now draw into a given bitmap
* content of SVG tag is written (used by the text tag)
* changed font handling in text element, still need proper alignment
* changed intersparse character of SvgTransformConverter.cs to space, because inkscape couldn't parse comma
* added class diagram for basic shapes

SvgUnit comparison seems not to be working so added IsNone() method to correctly identify a none type.

Now handles values of none without throwing an exception. This bug could cause images to load very slowly.

Applies default values of 50% for radial gradient cx,cy and r. This prevents an OutOfMemory exception when loading svg files without these parameters specified.

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- 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.

Removed some compiler warnings.

- Fixed a bug that caused <text/> elements to be parsed incorrectly, leading to exceptions within the document.

- Fixed #7986: public static SvgDocument Open(XmlDocument document) returns null: Implemented the proposed solution
- Added more XML API comments.
- Removed SvgVisualElementEvents.cs class - this was not used and not likely to be used

- Refactored SvgElementFactory to use the new SvgElementAttribute to get available elements.

This was accomplished by adding the new static method to the SvgRenderer class (as detailed in the work item) and a new Draw method overload that takes in a Graphics object as a parameter.

- Fixing #8494: Polyline fill being ignored. This appears to have been done on purpose (the Fill property was overridden to return null) but without reason. GIMP, Firefox 3 & Opera 9 all render the fill.