luatexja-preset.sty: using 'fontname' instead of filename

 * Removed obsolete option ('kozuka4' etc.)
 * Used fontname for Kozuka fonts (Pro, Pr6, Pr6N) and Yu fonts.
   - See TEXMFVAR/luatex-cache/generic/names/luaotfload-names.lua
   - Test needed: Kozuka (Pr6) and Yu (OSX)
   - If you have Hiragino fonts or Morisawa fonts,
     please edit luatexja-preset.sty to use 'fontname' of them.