change cpu temperature label from fahrenheit to celcius

[eshicks4]

the raspberry pi reports temperature in degrees celcius so fix the label to match. also a bit of cleanup because it was bugging me.

[chris-ccn]

The Obaintemperature (sic) function converts to Fahrenheit, though, so this change would not work with just an image swap.

[eshicks4]

The Obaintemperature (sic) function converts to Fahrenheit, though, so this change would not work with just an image swap.

Not what I'm seeing. I have everything on the Pi's set up for US standards and it still displays in Celcius. I'm perfectly OK with this but it just needs the F switched for a C in the graphic.