Initial cleanup after [29220]:

* Alter/remove some jQuery global selectors, views should only manage themselves
* Trigger an event for attachments when arrow keys are pressed: `attachment:keydown:arrow`
* `media.view.Attachments` should listen for `attachment:keydown:arrow`
* Favor scoped selectors over globals

See #23560.

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git-svn-id: http://core.svn.wordpress.org/trunk@29330 1a063a9b-81f0-0310-95a4-ce76da25c4cd