Replace WMI with PDH for WindowsCentralProcessor counters

[dbwiddis]

Committing the PdhUtil and intial implementation for CentralProcessor. Further implementations will come in later PRs.

[coveralls]

Coverage remained the same at 91.32% when pulling 44d2ba6 on dbwiddis:pdh into 317ca78 on oshi:master.

[codecov-io]

Codecov Report

Merging #507 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #507   +/-   ##
=========================================
  Coverage     83.94%   83.94%           
  Complexity      194      194           
=========================================
  Files            27       27           
  Lines          1395     1395           
  Branches        200      200           
=========================================
  Hits           1171     1171           
  Misses          104      104           
  Partials        120      120

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