JsonConfig, <limn> tag, updated to latest vega/d3 JS

* Base Limn on JsonConfig, which properly handles all
Json storage, caching, and complex NS registration
* Add <limn> tag (enabled with $wgEnableLimnParserTag)
to allow <limn>{...json...}</limn> in-page graphing
* Updated vega to 1.4.1 e8013b855ef8331d1a07b9ef266cc8fc2738e436
* Updated d3 to 3.4.11 a10b22654c9275da1050e1513bbd834646c0bde3
* Updated topojson to 1.6.15 ea2b20289120eb5a38132bdf0de8a6372d10f0b1
* Removed min versions - let resource loader deal with it

* TODO: Couldn't find the source for d3.geo.projection, removed for now

If you had some pages in Limn namespace, use this
configuration in your LocalSettings.php:

$wgJsonConfigModels['LIMN_DATA'] = 'limn\Content';
$wgJsonConfigs['LIMN_DATA'] = array(
    'namespace' => 44,
    'nsName' => 'Limn',
    'isLocal' => true,
);

Change-Id: I1e87c762d42c256bbf0d9d9aad96e56683e34898