[devices/ADXL345] Use BooleanView instead of RegisterView where sensible
[devices/ADXL345] Fix setting data registers from Fifo

* Replaced absurd left shift by correct right shift
[devices/ADXL345] Removed unneccessary unboxing
[devices/ADXL345] Removed obsolete out commented lines
Merge pull request #4 from ejoerns/pull-req/adxl345-fix

Fixes for the ADXL345 accelerometer device