* add GDI+ rendering support
* add GDI+ static rendering methods in HtmlRender
* add RenderToImage to existing image to act as background
* refactoring
* fix element height not respected
* fix index out of range exception in table layout (thx Kublia)
* fix floating point values handling
* fix mm and cm units factor
* fix table width not respected and incorrect unit handling
* fix error with empty lines and rtl
* add RTL html test sample