delete GasModel from monads in Toil/Monad.hs

add extra command witness to TxWitness

add TxCommand type and add it to Tx

delete useless Utxo/Monad.hs

refactor Command, mv gasPrice to Payload

integrate Pact into tx processing

redefine toJSON/fromJSON function for Payload

refactor CommandResult, only remains Gas

optimize the imports of mpt

add Mptree.StateRoot to PactState, because it changes in tx processing

init pact schema when state root is empty

renmae GStateDB for tx processing to MPTDb and move it to

add functions for applying command, used in tx processing

make GlobalToilM supports Pact stuffs

store root state in GenericBlockHeader and make LocalToilM supports Pact