As long as the functions AdjustForViewBoxWidth and
AdjustForViewBoxHeight are not fully developed pay attention that the
ViewBox width and height will not mismatch the positions of the marker
element then one of them are zero.

This changes are based on Issue #212 from mater.

Add: Quick solution to avoid  ViewBox width or height zero calculation.
Add: UnitTests

Create metafile rendering Unit Test based on Issue #210 from master.

This reverts commit a7097113.

This reverts commit 480a54d8.

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.