ExtJS 3.4.0

Added Sencha ExtJS-3.4.0  (GPLv3 licensed), this is a big library, added the *.js files and also the css/themes/images needed for it to work.

Source:
http://www.sencha.com/products/extjs3/download/
http://www.sencha.com/products/extjs3/download/ext-js-3.4.0/203

(in the repository already exists ext-core/3.1.0 which appears to be the same library but IMO there are files missing and the name is not correct, so I used another directory for this)