We must still initialize and clean up the legacy Trigger#timer

(cherry picked from commit da5620a4e8bbe6677b9f73303cf5cc735400576d)
Naming convention

(cherry picked from commit 6e9b7b7e64e601e654f43e3057b369483fa647a9)
Synchronize access to the ScheduledExecutorService so that we can avoid NPE's during failed startup and lazily initialize it safely.

(cherry picked from commit 9471274dcd912d12d8b80aaef28aa14e0733214d)
Null check

(cherry picked from commit 44f6367085a46ed78739db799cf96c9a3d52cf34)
Remove meaningless initialization

(cherry picked from commit c11c6cea34c8af39661ee513998e0e887443f31a)
[FIXED JENKINS-20800] HTML metacharacters not escaped in log messages.
(cherry picked from commit a900b488b527a25009e3536bc94e945f5fbfe4ad)

Conflicts:
	changelog.html
	core/src/main/java/hudson/Functions.java