cache the keytype to safe an extra smccall for every request.

this code is from smcFanControl
corrected the sensors for the macpro5,1

1. don't show second cpu info on single cpu systems
2. added ampere of the four drive bays
3. corrected the smc key id for the cpu temperature
4. removed redundant cpu package temperature
Merge pull request #252 from denis2342/master