[Sketches] fixes for FLASH write on Arduino

Need to handle the PROGMEM access in a separate write routine.

Signed-off-by: Christopher Hall <christopherhall.hsw@gmail.com>
[Sketches] tidy up EPD2 G2 driver interfaces

Signed-off-by: Christopher Hall <christopherhall.hsw@gmail.com>
[Sketches] fixes for demo2 for modified EPD2

Signed-off-by: Christopher Hall <christopherhall.hsw@gmail.com>
[Sketches] additional demos for the COG G2 panel

Notes:

1. command2 does not have an 'r' command since the G2 waveform does
   not need access to the old image.
2. tested on Arduino Uno and TI LaunchPad

Signed-off-by: Christopher Hall <christopherhall.hsw@gmail.com>