node hflip status not saved/loaded. #114

when a workflow is saved, if a node is placed horizontally flipped, that state is not saved into json, this causes when reload this workflow into canvas, the horizontally flipped node is no longer flipped and it's connected edges look twisted. so we need to:

1. when save, h-flipped state should be added to json just like breakpoint
2. for comleteness, let's add v-flip, rotation keys to json as well, even thought they will not be used at the moment
3. when load the workflow from saved file, needs to apply the saved json k-v pairs to reflect the flipped state.