Bumping elementtree version to 0.1.5 to match plugman and support namespaced xml elements
Fixes a bug where cordova prepare bombs on a config missing a content
element
  - Changes an undefined check to falsey to cover random null value
    returned from elementtree

  Tested By: David Kemp <drkemp@google.com> via Medic
[CB-4774] Updated prepare flow to make platform config.xml a build
output
  - Adds a new method to manually merge two config.xml files