Refactor trust view command into a --pretty flag on trust inspect

[n4ss]

Signed-off-by: Nassim 'Nass' Eddequiouaq eddequiouaq.nassim@gmail.com

- What I did

• Remove docker trust view which contains the same information as docker trust inspect but in a pretty-print format.
• Moved the pretty-print format feature to a --pretty flag on docker trust inspect (same as docker service inspect [--pretty]).
• Cleaned-up the pretty-print ouput format.
• Adapted the tests of docker trust view to test docker trust inspect --pretty instead with the new output format (some duplicates tests are now present because the two original commands had some similar tests)
• docker trust inspect --pretty (old docker trust view) now accepts several images as parameters to inspect (used to be limited to 1, but docker trust inspect accepts several images so we had to keep consistency)

- How I did it
For now (I'll refactor that later), docker trust inspect executes the old codepath if no --pretty flag is provided on the cli, otherwise executes docker trust view's codepath for each image arguments.

- How to verify it
$ make -f docker.Makefile test

and

$ docker-dev trust inspect [--pretty] nginx:latest redis:latest docker:dind

- Description for the changelog

• Moved the pretty-print format feature of docker trust view to a --pretty flag on docker trust inspect. The docker trust view has been removed.

[n4ss]

cc @vdemeester @thaJeztah @dnephin @endophage

[dnephin]

couple small nits

[dnephin]

go comments are generally done with // even if they are multi-line. /* */ is only used for package comments.

[dnephin]

same nit about comment

[dnephin]

some build failures as well

[codecov-io]

Codecov Report

Merging #934 into master will increase coverage by <.01%.
The diff coverage is 90.47%.

@@            Coverage Diff             @@
##           master     #934      +/-   ##
==========================================
+ Coverage   53.91%   53.92%   +<.01%     
==========================================
  Files         262      262              
  Lines       16601    16605       +4     
==========================================
+ Hits         8951     8954       +3     
  Misses       7050     7050              
- Partials      600      601       +1

[vieux]

LGTM thanks @n4ss!