ENYO-2732: Add proxy parameter in package download call

Tested on Linux within HP intranet. This PR must be tested behind a firewall requiring proxy setting to go on internet. Be sure to setup proxy parameters in `ide.json`. 

* ENYO-2732: Add proxy parameter in package download call

Enyo-DCO-1.1-Signed-off-by: Dominique Dumont <dominique.dumont@hp.com>