Allow processes to depend on each other

[ohuu]

Processes may require other processes to start before they can start. We should add a new property to the [[processes]] table called depends-on which takes a list of processes to start before the current process can.

[[processes]]
type = "baremetal"
name = "server"                      # Required - must be unique among ALL processes
command = "yarn dev" # Required
depends-on = ["db"]      # <---- list of other processes to start first