flips without pubsubs

This PR introduces the following changes
* Flips no longer use pubsubs, but are written in the database. This makes it easier to synchronize flips in intermittent wireless. Furthermore, these flips are encrypted using basic RSA encryption.
* The hub manager no longer blocks listening for channels.
* Basic RSA encryption/decryption in utils
* Serialization has been switched from json to CPickle, to remove any unicode to string conversion problems. This makes entries in redis slightly less readable.

Tested using the following script:
```
rocon_launch rocon_gateway_tests singlehub.concert
```