ENYO-3492: load proxy config from environment (if missing) 


* ENYO-3492: load proxy config from environment (if missing) 

Related JIRA: https://enyojs.atlassian.net/browse/ENYO-3492

Enyo-DCO-1.1-Signed-off-by: Dominique Dumont <dominique.dumont@hp.com>