Use the webapp API in Key Manager to store keys in server.

• "send_keys pseudocode"https://leap.se/en/docs/design/nicknym#Pseudocode
• "example of client code using the webapp api":https://github.com/leapcode/leap_client/blob/develop/src/leap/services/soledad/soledadbootstrapper.py#L222
• "webapp api spec":https://we.riseup.net/leap/leap-provider-api#put-api_base-users-uid-json

(from redmine: created on 2013-05-20, closed on 2013-05-21)