PollNY: version 3.0 - works with MW 1.21.1.

* New API module replaces the old AjaxFunctions file
* lightbox_light.js, an older version of LightBox.js, deleted
* moved to use local context instead of global variables where possible
* Removed some unused i18n messages, added a few new ones + message documentation
* Inline JS moved to the main JS file, Poll.js
* Swapped $wgScriptPath to $wgExtensionAssetsPath where appropriate
* Proper ResourceLoader support & usage across codebase
* Removed $wgPollScripts; unused & unneeded now