Added behavior: "Polling ignores commits with certain messages"
Added MessageExclusionTest test case.
Migrate to abstract. Added UserExclusionTest.
Optimize Pattern matching.
Fix help page. Not literal, but Pattern.
Don't use deprecated method.
Support multiline comments matching.
Extend description with multiline matching.
Findbugs should not warn about intentional null Boolean return in MessageExclusion

Since isRevExcluded intentionally returns null in all cases, and is
excluded explicitly in the other cases, it is safe to exclude it in
this new case as well.