Adds policy.apply method for applying policy

[justin1121]

Needed to move around the Policy class a bit to make this work. A little
more straightforward API.

[codecov]

Codecov Report

Merging #109 into master will increase coverage by 0.02%.
The diff coverage is 89.13%.

@@            Coverage Diff             @@
##           master     #109      +/-   ##
==========================================
+ Coverage   91.15%   91.17%   +0.02%     
==========================================
  Files          35       35              
  Lines         882      884       +2     
==========================================
+ Hits          804      806       +2     
  Misses         78       78              

Flag	Coverage Δ
#unittests	91.17% <89.13%> (+0.02%)	⬆️

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Impacted Files	Coverage Δ
cape_privacy/policy/data.py	82.92% <ø> (-3.52%)	⬇️
cape_privacy/policy/policy.py	93.96% <88.63%> (+0.21%)	⬆️
cape_privacy/coordinator/client.py	88.40% <100.00%> (ø)
cape_privacy/policy/__init__.py	100.00% <100.00%> (ø)

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