Migrate to Ext JS 6.0

From https://github.com/bjornharrtell/extjs

• Release ExtJS 4.2.1.883 by Jan 2014
• Release ExtJS 5.1.1.411 by May 2015 (+16 mois)
• Release ExtJS 6.0.0.449 by July 2015 (+18 mois)
• Release ExtJS 6.0.1.250 by April 2016 (+27 mois)