Removing NodeProperties when cloning slaves

Fixed so that NodeProperties that were auto populated
and then manually removed from the settings selector
page are actually removed on the new slaves when
cloning an existing slave.

Change-Id: I1c17792fdb4c4c61355bddd1c27ad6b2455b711e
Changed help text when adding slaves

A help text specific for editing existing
slaves is not visible when adding new slaves.

Change-Id: Iea2de928c969a5e3098c2f2f085ac78c62f8338e
Merge "Removing NodeProperties when cloning slaves" into internal
Merge "Changed help text when adding slaves" into internal
Added button for taking offline leniently

There is now an optional dependency to lenient
shutdown plugin, allowing admins to take slaves
offline leniently if the Lenient Shutdown Plugin
is already installed.

Change-Id: I6c55998900f2f4702b2b6dd91f048f026c332a6e