.Net 3.5 Support and Marker Fixes

- 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
Marker support. perserveAspectRatio Align support
New types/converters for markers and aspect ratio
Finished aspect ratio parser
Fixed ConvertFrom for orient and aspect ratio
Merge pull request #73 from Guymestef/master

Reading EntityReference on open when use as a node
added nuspec files
Improve SVG Support: TSpans, Paths, etc.

- 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
Merge pull request #75 from bcbarnes-gmx/Devel

fixed up the support for markers so that they draw properly, and added support for "preserveAspectRatio" except for the 'slice' and 'defer' options.
Descendants Extension and Metadata Tweaks

- 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.
updated version to 1.7
Merging with Official Project
Merge pull request #77 from erdomke/master

.Net 3.5 Support and Rendering Improvements (Markers, TSpans, Paths, etc.)
Fixing Build Errors
Revert ".Net 3.5 Support and Rendering Improvements (Markers, TSpans, Paths, etc.)"
Merge pull request #78 from vvvv/revert-77-master

Revert ".Net 3.5 Support and Rendering Improvements (Markers, TSpans, Pa...
Merge pull request #79 from erdomke/master

.Net 3.5 Support and Rendering Improvements (Markers, TSpans, Paths, etc.) + Working Build!
Support for 'slice' and fixed '...Max' in aspect ratio
Merge pull request #80 from bcbarnes-gmx/Devel

Support for 'slice' and fixed '...Max' in aspect ratio
Gradient Improvements

- Added support for the "gradientTransform" attribute on both linear and
  radial gradients. The matrix in this attribute needs to be applied to
  attributes with coordinate values on the gradient element in order to
  transform them into the correct coordinate space.

- Added support for a value of "pad" for the "spreadMode" attribute on
  both linear and radial gradients. This is the default value but was not
  implemented correctly. In order to implement, we examine the properties
  of the gradient along with the element to which the gradient is being
  applied to determine if we need to expand the bounds of the gradient to
  fill the element. If so, we do so and adjust the color stops and
  positions so they are correct for the new gradient bounds.

- Divided ISvgStylable into ISvgBoundable and ISvgStylable. The
  SvgUnit.ToDeviceValue method just needs bounds so it can take
  ISvgBoundable. Moved SvgDocument.GetDimensions() to SvgFragment and made
  SvgFragment ISvgBoundable.

- Fixed a bug in SvgFragment.PushTransforms where it was calling the
  SvgUnit.ToDeviceValue overload that takes no parameters. This overload
  doesn't work if the value being converted is a percentage. (The overload
  should probably be removed entirely, but we didn't take that on in this
  commit.)

- Fixed an issue in SvgGroup.Bounds where a child with empty bounds would
  cause the group's bounds to be reported as empty.

- Fixed broken build by adding missing SvgMarker.MarkerUnits property.

- Converted files that we touched with mixed tabs and spaces to spaces.
  Also removed unused usings from files we touched.

- Converted SvgLinearGradientServer to use properties without backing
  fields for X1, Y1, etc. in order to match SvgRadialGradientServer.

- Moved default value assignments into constructors for consistency.