lnd: modify the rpcServer's methods to use the new wallet API's
lnd: modify the rpcServer's methods to use the new wallet API's

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