[transfer] Add optional quantity in wallets list for random mode

[Montspy]

A wallets list is a wallet per line
Default is to send 1x NFT per wallet
LooPyGen could accept an optional quantity for each wallet line
wallet.loopring.eth,5 sends 5 random NFTs to wallet.loopring.eth
wallet.loopring.eth is still valid and is equivalent of wallet.loopring.eth,1