CB-5493 lazy_load now downloads to a temp dir and then moves.

If "cordova create" is interrupted with Ctrl-C while downloading the cordova
library for www, a bad version is stored in ~/.cordova/lib/. That bad version
is then used for future runs of "cordova create" which results in projects with
www dir containing no files except a subfolder named like
cordova-app-hello-world-3.2.0-ee9a86g3