initial import of epaper code from hexasense test firmware
extract often used spi send pattern to own function
remove non-functional declarations
first working version that doesn't kill the network stack
use knowledge of previous screen for refresh, use contiki wdt
wrap all epaper interaction into one function

this one function takes only the temperature of the display, and a
measurement of temperature and humidity to load an image from an
attached AT45 flash and write it to the display.
add explicit initialization to the epaper module

this should avoid spurious selections of the display/flash chip by
floating pins
remove debug spew
add epaper update function that doesn't always refresh the display

if called, only update the display if the last update was more than ten
minutes ago, or if the cumulative number if display updates since the
last refresh (including current) exceeds one.
broadcast to self should also send values to the epaper handler
don't redraw the screen on double-updates if the cumulative change is zero
implement endpoints for heater inflow/outflow sensors
do even less superfluous screen updates
Merge branch 'pb-pt100' into pb-emos

Conflicts:
	firmware/Hexabus-Socket/Makefile
	firmware/contiki-2.x/platform/Hexabus-Socket/hexabus_config.h
display special measurement values and screens on the epaper display

clamp measurements to some values (and maybe have special screens for
those) and add ability to display some special screens.
significantly increase display speed for special screens
add handler and endpoint for hexasense buttons
add feedback process for hexasense state
round measurements displayed on the epaper display instead of truncating
add simplistic "no link" detection

if the default router does not send HxB info packets for an entire
minute on it's link-local address, the link is assumed to be gone.