Added two generic display drivers and two drivers for monochrome OLED displays

Makefile

_examples/display_er_oledm028/display_er_oledm028.cpp

_examples/display_er_oledm028/display_er_oledm028.h

_examples/display_er_oledm028/main.cpp

_examples/display_ly091wg14/main.cpp

drivers/display_generic_1bpp.cpp

drivers/display_generic_1bpp.h

drivers/display_generic_4bpp.cpp

drivers/display_generic_4bpp.h

drivers/display_ly091wg14.h