Reorg the batch system slightly as per Eric's request that batch mode
experiments look more like regular experiments. Batch mode experiments can now be preloaded and swapped. When preloaded, they go into a "Pause" state. Swapping a batch mode experiment in puts them into the "posted" state so the batch daemon will see them. Swapping out a batchmode experiment does the expected; it puts them back into the Pause state. Terminating a batch mode experiment does the expected; its gone. When a batch mode experiment finishes normally, it goes back into the pause state, which allows batches to be reinjected as many times as Eric likes.