New set of skins for HP Prime Virtual calculator

[Spybot]

Hi calc_freak!

Yes, believe me I tried for the vertical version several different screen sizes (maintaining the aspect ratio) between the small and the medium size, but all of them showed things incorrectly, I don't know if it's a glitch from the emulator or something. So I decided to assign the original 320 x 240px screen size to the vertical version, this size does show things perfectly fine as well as the 640 x 480px for the medium size and the 960 x 720px size for the large version.