Use key fingerprint as ID instead of “long” ID.

[Natureshadow]

It is generally assumed that for applications demanding good security, the full key fingerprint should be used instead of just the 64-bit or, let alone, 32-bit key ID.

This PR uses the key fingerprint from GPG to replace the key ID. It works by waiting for an fpr record in the key list and, if it looks like belonging to the key at hand by comparing the end of the fingerprint to the previously found ID, replacing the key_id field with it (it should normally be the next line after the pub or sec record).

As a bonus, this increases compatibility with other frontends, like gopass-pw, which use the fingerprint and would cause unwanted updates of .gpg-id.

[coveralls]

Coverage decreased (-0.003%) to 7.151% when pulling 255f6e2 on Natureshadow:gpg-use-fpr into 1ad0648 on IJHack:master.

[codecov]

Codecov Report

Merging #452 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master    #452      +/-   ##
=========================================
- Coverage    7.23%   7.23%   -0.01%     
=========================================
  Files          41      41              
  Lines        2722    2724       +2     
=========================================
  Hits          197     197              
- Misses       2525    2527       +2

Impacted Files	Coverage Δ
src/pass.cpp	4.61% <0%> (-0.08%)	⬇️

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