Add context switches & interrupts

[jpbempel]

Add 2 methods in CentralProcessor interface
only Linux implementation provided for now

[codecov-io]

Codecov Report

Merging #447 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #447   +/-   ##
=========================================
  Coverage     83.35%   83.35%           
  Complexity      191      191           
=========================================
  Files            27       27           
  Lines          1376     1376           
  Branches        200      200           
=========================================
  Hits           1147     1147           
  Misses          109      109           
  Partials        120      120

Impacted Files	Coverage Δ	Complexity Δ
.../src/main/java/oshi/hardware/CentralProcessor.java	100% <ø> (ø)	0 <0> (ø)	⬇️

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[coveralls]

Coverage remained the same at 91.2% when pulling 6514391 on jpbempel:master into 5cfcf14 on oshi:master.

[dbwiddis]

Is this not applicable/available for other OS's? I'm worried about committing code for only a single OS without a path to trying the others (if possible). Should also file an issue to track this if possible.

You need to implement the new methods in the JSON version as well.

[jpbempel]

Added windows implementation, but cannot test on other systems like Mac/Solaris/FreeBSD
However tips for this can be found in https://github.com/giampaolo/psutil/blob/master/psutil/_psutil_osx.c#L1774

Thanks