Change cordova serve's project.json to include etags.

Allows App Harness to only update changed files.
CB-5368 Cordova serve deflate content breaks IE

Switching the order so that we normally offer gzip instead of deflate.
http://stackoverflow.com/questions/1077869/internet-explorer-8-deflate
CB-5377 serve: should only indicate listening when it is
Fix issue not finding platform script when in subdir
- check platforms which have subdir
- append subdir to libDir for detected platforms
CB-5364 config_parser - check for null element text