More plugin unit tests

Filling out line level coverage for pluginhost. Not sure why Plugin.Base isn't showing up in the reports. It's tested in the same batch of tests

Fixed Plugin errors, following BaseCore refactor, when using Y.Base.create to extend Y.Plugin.Base. Fixes #2531663 Modified plugin base unit tests to use Y.Base.create for one of the test plugins, instead of Y.extend.

Prepped tests for coverage reporting

Changed the plugin destroy test back to normal. See #2529568

fixed test

postponed nested after listeners still execute if when unsubscribed if they originally were supposed to fire.

Added name to basic test case, to avoid guid being used

Pulled in modified tests (names, no console) from 3.1.0+ branch

tests cleanup (yui- to yui3-)

Added host destroy test case

Plugins now destroyed correctly, when host is destroyed. Fixes #2528388