0026298: Visualization, OpenGl_Text - make font resolution configurable.

0026298: Visualization, OpenGl_Text - make font resolution configurable.
Add THE_DEFAULT_RESOLUTION static const parameter to Graphic3d_RenderingParams.
Add resolution to Graphic3d_RenderingParams.
Drop redundant variables from OpenGl_Workspace.
Add a new parameter to Graphic3d_GraphicDriver::TextSize method (and to OpenGl_GraphicDriver).
Add a new parameter to OpenGl_Text::Render() and to OpenGl_Text::render() methods.
OpenGl_Text::FontKey() considers a resolution (PPI) now.
Add a new argument '-resolution' (sets a pixel density) in the 'VRenderParams' draw-command.