src: Made sensor publish and display rate configurable

The symbols SENSORS_PUBLISH_RATE and SENSORS_DISPLAY_RATE can be used to
set the rate at which data from sensors is published and refreshed on the
display.
pcb: Fix some pads being only on one side of the PCB

Pads on the screw terminals and 2.54mm headers were only on one side of the
PCB.
pcb: Changed wrong resistor value

Value of the Ethernet termination resistors used was 49k9 instead of 49.9.
pcb: Added schematic in PDF format

Plotted schematic in eeschema to PDF.