specs: Rename /ping to /finger

This is to make it clear that this isn't keepalive but rather a way to
figure out whether you're authenticated and what the API version is.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
rest-api: Update operations API

 - Use UUIDs instead of IDs (since they don't persist)
 - Return a standard collection (list) instead of dict

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
rest-api: Add networks API

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Merge pull request #70 from stgraber/master

Some REST changes