ENYO-3492: load proxy config from environment (if missing)
ENYO-3492: added globalProxyUrl parameter in ide.json
ENYO-3492: document proxy setting in README.md
ENYO-3492: added globalProxyUrl example
Merge pull request #696 from enyojs/ENYO-3492

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