Ubuntu apt packages

- [x] Get fpm creating a working apt package
- [x] Publish apt package to s3 as apt source so it works with apt-get install
- [x] Handle upgrades
- [x] Handle uninstalling the agent
- [x] Allow the agent to start from a config-file
- [ ] CDN apt.buildbox.io
- [ ] HTTPS apt.buildbox.io
- [x] Handle the agent version throughout the packaging process
- [x] Sign the packages with a key

```bash
# You need to be sudo
sudo su

# Add the repository to your APT sources
echo deb http://apt.buildbox.io/buildbox-agent unstable main > /etc/apt/sources.list.d/buildbox-agent.list

# Then import the repository key
apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 5a7dbc2d7109e367

# Install the agent
apt-get update
apt-get install -y buildbox-agent

# Add your agent registration token
sed -i "s/xxx/[insert agent access token here]/g" /etc/buildbox-agent/buildbox-agent.env

# Then you start the agent
service buildbox-agent start

# If you want to start more agent instances
cp /etc/init/buildbox-agent.conf /etc/init/buildbox-agent-2.conf
service buildbox-agent-2 start
cp /etc/init/buildbox-agent.conf /etc/init/buildbox-agent-3.conf
service buildbox-agent-3 start
# etc.

# View the logs at
tail -f /var/log/upstart/buildbox-agent.log
```

This installs the agent to: `/usr/bin/buildbox-agent`

Agent configuration can be done in:

- `/etc/buildbox-agent/buildbox-agent.env`
- `/etc/buildbox-agent/bootstrap.sh`

Builds will run inside:

- `/var/buildbox-agent`

Pid can be found:

- `/var/run/buildbox-agent.pid`