A multisig wallet implemented in Func and command line interface in Fift.

Some addition:
- there is a bug in `list_orders_unsigned` get-method that I fixed after submission.
` orders.udict_get_next?(32, order_id);` starts with order_id equal to -1. But it MUST starts with 0 to skip the special value in order book.

- message layout of smc is described at `multisig-wallet-code.fc`. Read this short description to better understand what is happening.

- `order_id` is a last 4 bytes of hash of order:
order_id = hash(expiration, seed, order_transfer_msg) >> 224.

2^32 is a good entropy to avoid collisions, but if it isn't enough we can easy increase to 6 bytes/8 bytes.

`seed` guarantees that the orders with same amount and address can be created again separately.

plus:
All required features are implemented.
Good performance (0.074G for a transfer with n=16, k=10).
accept_message() is called only after one signature was verified.

minus:
seqno is not included in a hash. The same order could be easily executed multiple times.

You check signature over msg_body which does not include seqno. I can surely take any past message, replace seqno with new and feed it into contract. Am I right?