Add plumberendpoint skelleton class

Change-Id: I1a9953a0634092181a1961298bfade87619741bc
Remove useless properties

Change-Id: Ibbd75b63ab6909cffad58a11f94893d88cb8f75b
Start sctpserversrc elements when going from NULL to READY state

Change-Id: I346b12f6c7e998ef97ef0b1291181cbe3b537cb3
revert commit 16ce2787d8000cc95be506d978b8ba5825cc329a

gstsctpserversrc: Block until the client is connected before going to PLAYING

Change-Id: I1ecd652462f71736ef1c6993849f84f397f6ba6b
plumberendpoint: Link valves to sctp client elements

Change-Id: I73177eaa15ed56ab6b2fbb5a73ab870c193a29a0