Rename meta-data.d to juju-info.
Drop juju-info directory, make it a json file instead.
Use a dict comprehension (from fcorrea's review).
No need to filter empty values.
Merged lp:~ack/charms/precise/landscape-client/separate-juju-info [r=fcorrea,tribaal]

Replace the use of meta-data.d for juju information, putting them in a landscape-client $data_path/juju-info.json file instead.