Add new class Font_BRepTextBuilder for generation of formatted BRep text.
Delete method Font_BRepFont::RenderText(), which should be replaced by Font_BRepTextBuilder::Perform().
for usage without OpenGL.
Split OpenGl_TextFormatter into Font_TextFormatter and OpenGl_TextBuilder.
Font_TextFormatter can format a text independetly of OpenGl now.
OpenGl_TextBuilder generates primitive array required for rendering text
using OpenGl_Font instance.
