thinknode_m8: initial support
adds some functionalities to ui_task and epddisplay:
epd display,
- supports screen off, and clear screen
- supports forcing full refresh every N partial refreshes (off by default, configured to 60 for M8)
ui_task
- UI_SHOW_CLOCK flag to display clock on first screen
- rotary button can act like joystick (with regards to Enter key), defaults to old config for existing nodes
- screen off on long press when using rotary button (very handy for the watch)