* 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.

- Fixed "#7845 - Arc Path Renders incorrectly" as described in the work item - W3C example now renders   correctly.
- Ensured that a divide by zero exception could not occur during rendering of stroke dash arrays.

- Changed the ISvgStylable interface StrokeDashArray property to be of type SvgUnitCollection instead of     SvgUnit[] and updated SvgGraphicsElement to implement this change.

- Fixed "#7522 support rotate(angle,cx,cy)". Added new properties and a new constructor overload to   SvgRotate in order to support the optional parameters.
- Removed redundant code from SvgElementFactory.

- Fixed [workitem:7526] whitespaces \t \r \n in path and points result in exception. The   SvgUnitCollectionConverter (SvgUnitCollection.cs) class had to split on \r, \t and \n aswell as ' ' and ','.

- Added SvgMatrix, SvgShear and SvgSkew missing files from the previous check-in.

- Made all transforms (SvgTranslate, SvgMatrix etc) sealed types.

- Fixed #6324: SvgElement.PushTransforms and ViewBox - not necessarily related to ViewBox but every   element was 'resetting' the current graphics transform if the element contained it's own transform. This 
  was a very small fix for a large problem (SvgElement.PushTransforms Matrix transformMatrix = new   Matrix(); changed to Matrix transformMatrix = renderer.Transform; in order to inherit the current   transform.)
- Fixed #6344: Parsing document incorrectly parents elements when it encounters empty nodes which are   in a different namespace. Empty nodes are now ignored and current nodes are closed as required. We'll 
  see how this fix goes.
- Fixed #6381: Units in inches are incorrectly parsed as millimeters - problem was caused by some   copy/paste work.
- Graphics has been replaced by SvgRenderer. This is essentially a wrapper around graphics but will allow
  custom svg related properties in the future when needed.
- Removed ISvgRenderer: A concrete implementation is suitable.
- SvgElement.ElementName has been changed to non-virtual and is set by the parser instead of the   developer having to specify it when developing the class.
- Added more XML API documentation.