Preserve initial packet order on sending

Current implementation sends out whatever is ready first, messing up the specified order by the programmer.
Remove legacy code for handling downstream components not being ready

Checking for downstream readiness was initially a problem as described in #40. That was due to initial packets being sent before the network is ready. It's partially solved in #69 when initial packets are only sent upon the respective network has been loaded. This PR solves the other half which is initial packets being sent in order of the programmer's specification so by the time the network is run, everything should be ready anyway.
Merge pull request #73 from kenhkan/preserve_order_of_initial_packets

Preserve initial packet order on sending