xmpp: Update Javascript XMPP Client to >= 3.0.0

Created by: SunilMohanAdapa

The current version of JSXC in FreedomBox/Plinth is 1.0.0 due to this version being available in Debian. However, 3.0.0 is available with lot of improvements. Update version in Debian and Plinth to >= 3.0.0.