Add GeoExt 1.1 geospatial JS lib

GeoExt, http://geoext.org, is a common framework for building geospatial (GIS) web mapping clients using JavaScript. GeoExt is based on OpenLayers (http://openlayers.org, hosted in CDNJS) and Ext JS (http://sencha.com v3, also hosted at CDNJS). See the GeoExt homepage at http://geoext.org : *GeoExt brings together the geospatial know how of OpenLayers with the user interface savvy of Ext JS to help you build powerful desktop style GIS apps on the web with JavaScript.*

GeoExt is BSD licensed https://github.com/geoext/geoext/blob/master/license.txt and has currently no CDN hosting. Note that also Ext JS licensing applies when Ext JS is distributed: http://trac.geoext.org/wiki/license. 

Package was downloaded from  http://geoext.org/downloads.htm, as full package: 
https://github.com/downloads/geoext/geoext/GeoExt-1.1.zip
Examples and documentation were left out of this pull. They are online respectively at:
http://geoext.org/examples.html and http://geoext.org/docs.html