Add upgrade-charm hook for moving Juju from metadata.d into JSON.
Rename variables, add some comments, debug from testing in local environment.
Merged from testing repo
Address free's feedback:
 * Add unit tests
   * Add Makefile with test and lint targets
   * Remove chown'ing of juju-info.json to facilitate testing
 * Extract migration code from generic upgrade-charm hook
Refactor into setUp
Add docstring to upgrade_charm.
More feedback from BjornT: make mea_data_path easier to grok, use dict not {} for fromkeys
Address Free's feedback - use real Configuration instead of a stub
Separate creation of config from setting up of old juju info.
Avoid re-using the juju_info variable name
Merged lp:~adam-collard/charms/precise/landscape-client/upgrade-charm-hook [r=free.ekanayaka,bjornt]

Add an upgrade-charm hook which will move any Juju information found in the old metadata.d directory into the new juju-info.json file.