chango to full Buffer Mode, remove picture loop,
because it's not worked.
look: https://github.com/olikraus/u8glib/wiki/tpictureloop
snprintf + public vars
- dispPowerSafe => true: PowerSafe Mode on
- dispLogo => true: showing Logo upper right corner
- dispContrast => possible to adjust the Display Contrast
change in date time, buffer deleted
Display-Constructor changed, reset goes to front
Arrow and Logo only shown, when production is on
Refactor OLEDDisplayClass to DisplayGraphicClass
