[JENKINS-14495] Refined fix - needed to pull uniqueness check out of apply() fn in case we were being passed an Array of nodes.
Fixes test failures introduced by  dbb100da, and adds a test for it now that I know it can be done.

Unlike [JENKINS-14514] this is a true fix rather than a workaround (now removed), and is more general.
cjo9900 discovered that behaviors were being redundantly registered (as of 1.474 the monolithic JS is broken up);
this caused some behaviors to be run repeatedly on the same elements, breaking reasonable expectations of some behaviors.
The ideal fix would be to change Behavior.register to be idempotent: for example, key it by selector, then maintain a set of distinct behavior functions for each.
Unfortunately some adjuncts directly call Behavior.list.unshift, bypassing register(...), which would be tricky to intercept (would need to make a mock of Array).
The known one cases are in core, but it is possible plugin adjuncts do this too, in which case it would be incompatible to (say) change the Array<Map<String,Behavior>> to a Map<String,Array<Behavior>>.
Instead, permitting redundant registrations as before, and just silently skipping all but the first at runtime when applying behaviors.
Beware that since adjuncts are loaded from multiple places, different JS function objects are registered each time, so a naive set of behavior functions does not work;
have to identify functions by their toString in order to ensure that each is run only once.
(Currently once _per selector_, conceivably >1x per element; could if necessary be refined to make sure a given behavior is only run once on a given element during one call to applySubtree even if the element matches multiple selectors.)

launching windows managed slave

Displays transient user actions in the User sidebar
Displays UserProperties that are also Action in the User sidebar

[JENKINS-11739] Cannot compile a plugin with a Plugin subclass in the same package as a package-info.java.
(Not quite FIXED yet since org.kohsuke.stapler.jsr269 seems to suffer from a similar bug, currently printing ugly warnings.)

[FIXED JENKINS-13916] Text parameters are now defined and shown in a textarea instead of a one line textbox.

Update transient action after config submit, as trantient action may change due to change of view properties.