add a --serialized-config flag

[opalmer]

In some circumstances the agent will need to be restarted. The problem currently is that if you have a command line flag, --ram, that is only part of the start target you need to be sure the old value is carried over when 'start' is called again. What we'll probably end up doing is provide a --config flag of some sort that can:

• serialize the current configuration object to disk
• pass in the configuration to the start target
• load in the serialized data into the configuration object

This means that in many cases extra command line flag won't need to be duplicated into targets where they don't make sense.