Resolve "add date attached to each payload" & "sequential read on payload array"

• change string payload in model.Node to struct
• add date to Payload struct
• add sequential read on payload array if randomAccess not set
• move random access to pushDataPayload()
• init node.NextPayload & node.RandomPayload
• update all scenarios in resources/scenarios to reflect new params
• update doc in doc/content with "Very QuickStart"
• test
• don't forget src/lorhammer/main.go default model.init{} creation

Closes #37 (closed)