Cloudutils: skyDrive, googleDrive, dropbox

* Module cloudutils added to invenio with support for googleDrive,
  skyDrive and dropbox. All cloud services are implemented using
  pyfs as the base class and are represented as an complete filesystem.
Cloudutils: Code cleanup

* Fixing some small bugs and cleaning up the code. Every file now
  has the appropriate header.
Cloudutils: files macro

* cloudutils_files.html now uses config file and not hard-coded
  service names.
Merge branch 'cloudutils' of https://github.com/w-is-h/invenio into cloudutils

Conflicts:
	modules/cloudutils/etc/templates/cloudutils_files.html