added a 'namespace' of HTMLViewer to PixelsPerInch, PointsPerInch, and P...

Added a "namespace" of "HTMLViewer" to the consts PixelsPerInch, PointsPerInch, and PointsPerPixel, because these consts are turned into #_define's in the generated C++ .hpp files, which makes it impossible to use PixelsPerInch anywhere else in any of the components in the project.

I install HTMLViewer into my C++ environment, along with TRichView and TRichViewActions, which also access HTMLViewer.  However, without this change, the #_define's conflict with "PixelsPerInch" used elsewhere in the project.  By making the consts names less generic, I am able to avoid the conflict.