Based on Issue #204.
Now users can add customer fonts/ private fonts to
SvgElement.PrivateFonts.

Unit Test:
Add Test: PrivateFontsTest
Add Resources from PrivateFontsTest.
Add SvgTestHelper
Change MultiThreadingTest, now based on SvgTestHelper to use shared code
(no code duplication)

Note:
MuliThreadingTest TestFile is not available. The vvvv/master should add
the test file to the resources or other developer can not test the svg
engine.

Load an attribute only once if possible.

Update to fix Draw(Height,Width) overload
#211 by OperatorOverload
Pull Request from master

Split by comma, remove space in the end
#209 by ifcwebapp
Pull Request from master

Add: SvgShapeRendering, SvgTextRendering and SvgImageRendering in
SvgAttributeCollection.IsInheritValue

Fix:
Now the application make sure to set back the old culture even an error
occurred.
SvgColourConverter.ConvertFrom
SvgPathBuilder.ConvertTo
SvgDocument.Write
SvgExtentions.GetXML

Add:
Attribute: "shape-rendering"

Change:
- Many other properties were unknowingly overloaded. I changed them to
override.
- Some methods or structures need the [CLSCompliant(false)] Attribute.
For example the Enums.TryParse extension. This extension has the where
condition IConvertible. IConvertible is [CLSCompliant(false)] and that
the reason why it is correct to mark the Enums.TryParse extension also
as [CLSCompliant(false)].
- Property "float Opacity" in SvgElement was unknowingly overloaded in
SvgGradientStop as string [stop-opacity]. In the end this property was
only used as float. I changed the SvgGradientStop.Opacity property from
string to float and to override.

Fix calculation of rectangle path

Fix #176: Blurry text when overlapped with colored background

W3CTTestRunner: Added a console log at the bottom to avoid annoying m…

The rectangle path width/height was computed using the full stroke width.
It should have been using the half stroke width instead.

W3CTTestRunner: Added a console log at the bottom to avoid annoying message boxes popups and to have a log to copy with a contextual menu to easily report errors.

W3CTestRunner: Added the code to infer the right directory separator …

W3CTestRunner: Added the code to infer the right directory separator for the current OS. Now doesn't crash anymore on Mac OSX.

Fix #185: Multiline text is not rendered. 

Fix #185: Multiline text is not rendered. Tspan is nested/child element to text element and it was not considered for path

Fixed problems when running in multiple threads

Fixed problems when running in multiple threads. The use of a static matrix and the use of StringFormat.GenericTypographic seemed to cause problems when used in multi-threading. This is resolved by making the matrix non static and use a copy of the StringFormat.

Also created a new exception for memory overflows. When using multithreading to render a large amount of big images the bitmap creation can fail (due to memory allocation) throwing an error. This is now caught and a specific exception is thrown.

Fix to #173: Sub elements in group element are not rendered

Extended the Marker start/mid/end getters to return null if none

Extended the Marker start/mid/end getters with a function to return null if the property was set to none. This will prevent nullpointer issues when having none as one of the items.

Added new Draw method

Skip to consider Symbol element directly, because it is calculated through reference from use element

Fix #55 : Call Path in a SVG with an empty content element causes an InvalidArgumentException[updated]

Infinite loop in SvgRadialGradientServer CalcScale

Fixed viewbox transaltion when altering the aspect ratio