Bug 1083410 - Implement means to obtain a W3C manifest
Merge branch 'w3c_manifest' of https://github.com/marcoscaceres/gecko-dev into w3c_manifest

* 'w3c_manifest' of https://github.com/marcoscaceres/gecko-dev:
  Bug 1083410 - Implement means to obtain a W3C manifest

Conflicts:
	dom/manifest/ManifestObtainer.jsm