Restore the system daemon

[daonb]

We need webexec to start automatically on boot.
We need to support both linux and darwin. The daemon will have to run as root and function as a gateway for all users on the system.
When a client connecys to the daemon, the daemon will spawn a neww user
agent for the client and use webexec accept to establish a connection.

[daonb]

It's a good opportunity to take care of #99 too