added xe-core

this is common js, css, of xe-core(Xpressengine).

All js and CSS file is minifed.(but comment is left becasue of license issue)

i set auto update for .js .css
https://github.com/xpressengine/xe-core
http://www.xpressengine.com (offcial site, Korea)

License : LGPLv2

P.S
this is new version of pull issue #954
Looks good... Can you put this one in a seperate pr thanks!