Add new execute services to the rspec
@ricci proposed adding a "reconfig" execute service, that would be run when a node is added or deleted. This could be a per-node service or a per-experiment service, needs more thought.
@gtw mentioned that we are using the old startup command, that is run on every boot. We should consider adding the ability to use the program agent based startup command, which is run at the beginning of event time (so only once). Perhaps option to either or both.