[FIXED JENKINS-20008] Added DirectlyModifiableTopLevelItemGroup.
ItemListener.fireOnDeleted
Noting API anomaly.
[FIXED JENKINS-18028] Providing a supported way to move an item between folders, firing changes as we go.
Working on making it straightforward for plugins to update even relative names after a move.
Rewrote computeRelativeNamesAfterRenaming to work with moves.
[FIXED JENKINS-18680] Update members of a ListView using a regular listener, not View.onJobRenamed which does not work with folders.
Items.move should return the new item.
FileUtils.moveDirectory falls back to copy-and-delete if target does not yet exist, which fails to work correctly with symlinks.
Merge branch 'master' into folder-moving

Conflicts:
	core/src/main/java/hudson/model/Items.java
Merge branch 'master' into folder-moving
More meaningful parameter/local variable names.
[JENKINS-18678] [JENKINS-18028] Confirming (as suggested in #1069 by @oleg-nenashev) that build history is retained after a move into a folder.
[FIXED JENKINS-20008] [FIXED JENKINS-18028] [FIXED JENKINS-18680] #1069: support for moving jobs into or out of folders.