[CS (System Info)] Allow OEM info

Checks if "data/oem/info.txt" exists and has text in it, if so it will display it up to 50 characters, and also checks if "data/oem/oem.png" exits and if so it will display it instead of the Cinnamon image
This might be nifty for commercial oem installs, or businesses

Edit: Should the locations be different, e.g "/usr/lib/linuxmint/common/" so MATE and XFCE can do somthing similar?