lnwallet: separate channel state into new struct
lnwallet: separate channel state into new struct

* Will be integrated into ChannelReservation also
* This is the struct that will be persisted to disk

bryanvu/lnd,BitfuryLightning/lnd,AndrewSamokhvalov/lnd,AndrewSamokhvalov/lnd,bryanvu/lnd,aakselrod/lnd,BitfuryLightning/lnd,ddustin/lnd,LightningNetwork/lnd,LightningNetwork/lnd,ddustin/lnd,aakselrod/lnd