Ghostscript.NET 1.1.9

Fixed problem with the PDF invisible layers (the optional content groups which will be left unmarked if process_trailer_attrs is not executed). Fixed text rasterization problem for some pdf's, it seems that the 'pdfopen begin' did not initialize everything required to render pdf properly so we replaced it with the 'runpdfopen' method which corrects everything (problem reported by "xatabhk"). Changed GhostscriptRasterizer methods to support Stream insted of the MemoryStream. Fixed handling files without the extension in GhostscriptViewer and Rasterizer.