[FIXED JENKINS-18807] Ignore SCM triggers which ask to suppress post-commit hooks.
Requires 1.493+, so just update to 1.509.x already.
Stylistic cleanups.
s/XXX/TODO/g
Greatly simplified POM.
Removed <reporting> section (no one runs reports on a plugin);
deleted unused or redundant dependencies;
deleted overrides of things now declared in plugin parent POM;
made various minor corrections and updated.