Less comments and per job success/failure messages

[ffissore]

This PR introduces a "useDetailedComments" flag: originally when plugin misses rights to changing PR status, it replaces it with comments, leading to many spam emails. This flags silences those emails, leaving just the success/failure ones.
It also introduces per job success/failure messages: it's also possible to use jenkins environment variables in those comments, as they get expanded.
Such comments are sent based on the state of the build and no longer on the presence of a publishedURL.

[ffissore]

This PR:

• mitigates https://issues.jenkins-ci.org/browse/JENKINS-22202
• solves https://issues.jenkins-ci.org/browse/JENKINS-24590 by exposing variable ghprbPullId to the comment
• should solve https://issues.jenkins-ci.org/browse/JENKINS-22608

[cloudbees-pull-request-builder]

plugins » ghprb-plugin #176 SUCCESS
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[ffissore]

Example message: arduino/Arduino#2279 (comment)

[jenkinsadmin]

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[ffissore]

Code has been rebased on current master 1f57cd8

[DavidTanner]

Are you sure you want the detailed flag to only be defined for all jobs? Or did you want that on a per job basis?

[ffissore]

I kept them in the singleton because much of the conf was there and because verbose comments were active for all jobs. Sure I would disable such verbosity by default and enable it only on a per job basis.