Increment transaction index

[DariuszDepta]

closes #36

[kulikthebird]

Let's try to:

1. Make inc_transaction_index and set_transaction_info methods take self as mutable ref,
2. Get rid of the RefCell for TransactionInfo,
3. Change the transactional method into something like:

pub fn transactional<F, G, T, ExecC, QueryC>(base: &mut dyn Storage, action: F, increment: G, wasm: &mut dyn Wasm<ExecC, QueryC>) -> AnyResult<T>
where
    F: FnOnce(&mut dyn Storage, &dyn Storage, &mut dyn Wasm<ExecC, QueryC>) -> AnyResult<T>,
    G: FnOnce(&mut dyn Wasm<ExecC, QueryC>),
{
    let mut cache = StorageTransaction::new(base);
    let res = action(&mut cache, base, wasm)?;
    cache.prepare().commit(base);
    increment(wasm);
    Ok(res)
}

EDIT: Or instead of FnOnce(&mut dyn Wasm<ExecC, QueryC>) => FnOnce(&mut Router<Bank, Custom, Wasm, Staking, Distr, Ibc, Gov, Stargate>)

[DariuszDepta]

To implement this functionality properly, some more (re)design work is needed in MultiTest. As this change has a low priority, I am closing this PR without merging,