debian: Fill in gecos field for jenkins user

Otherwise when Jenkins runs git, git will complain that the identity is
not set up correctly and will fail.
[JENKINS-3107] Expand an Advanced section if some fields are already customized.
Initial implementation handles only text fields, not e.g. checkboxes.
[JENKINS-3107] Rather than preëxpanding the Advanced area, just show an icon.
[JENKINS-3107] IE 9 fix.
[JENKINS-3107] Icon looks better before button rather than after, for reasons of alignment with the rest of the form.
Trying to demonstrate how to use some more advanced databinding. No luck so far.
Removing debug text.
Apparently cannot have a repeatableHeteroProperty not inside a section/block.
instance, not it.
Get choices from descriptor.
Immutability & copying of lists.
Better formatting.
[JENKINS-19004] set name of remoting threads
[JENKINS-16178] Add builds that were run by user to user's build list.
Add test for PR #909
Add changelog recoed for PR #909
plexus-classworlds 2.5.1
Log CannotResolveClassException and similar at FINE, not WARING.
OldDataMonitor already collates these errors and presents them to the user with a fix.
Printing a stack trace for each and every missing class just clutters the log file.
(Especially when restarting after disabling a widely-used plugin.)
Merge pull request #895 from kutzi/JENKINS-19004-channel-executor-name

[JENKINS-19004] set name of remoting threads
[maven-release-plugin] prepare release jenkins-1.528