Ref #1117
To complete all three features in command blocks, we can change the adjacency of blocks to the relationship in cart linking. Thus, the need for a command that link carts emerge.

Eh, we can probably use /entitydata, need to make sure it works

@CovertJaguar To link with command, it still is a bit difficult: you need to do
/entitydata <uuid of cart a> {ForgeData:{rcLinkAHigh:"<uuid high of cart b>"}}
/entitydata <uuid of cart a> {ForgeData:{rcLinkALow:"<uuid low of cart b>"}}
And vice versa for the other cart; moreover, both link should be checked. This might be a good addition, but I will reopen it if someone requested it.

Eh, should not have pinged CJ.