Add quick_sign_key function, add hidden recipients to encrypt_file, and allow paths in verify_file

[zach-zetier]

• Added complete new function quick_sign_key with unit tests.
• Added hidden recipients to encrypt_file function.
• Updated verify_file to take a path (str) or file object (IO) as comment block states.

[codecov]

Codecov Report

❌ Patch coverage is 94.44444% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.97%. Comparing base (efb2043) to head (6ed2c6e).
⚠️ Report is 51 commits behind head on master.

Files with missing lines	Patch %	Lines
test_gnupg.py	93.75%	3 Missing ⚠️
gnupg.py	95.83%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #275      +/-   ##
==========================================
- Coverage   95.21%   94.97%   -0.24%     
==========================================
  Files           2        2              
  Lines        1819     1971     +152     
  Branches      177      182       +5     
==========================================
+ Hits         1732     1872     +140     
- Misses         43       55      +12     
  Partials       44       44              

Flag	Coverage Δ
unittests	94.77% <94.44%> (-0.39%)	⬇️

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