Make NEP-11 code use getnep11balances the same way NEP-17 code uses
getnep17balances. This command was introduced well before getnep11balances
appeared, so it required always specifying contract explicitly. Now this
constraint can be relaxed somewhat in most cases.
1. In the single token mode compare known hashes instead of names, names can
be misleading.
2. Hardcode NEO/GAS, they are special (if not overrided by the wallet data).
We have this data available since 0.99.1 while all public networks require at
least 0.99.2 for compatibility and NeoFS setups use 0.99.2+ too. This data can
simplify account handling considerably making additional requests unneccessary
in many cases.
In the same way we do for NEP-17 tokens. This code predates "getnep11balances"
call, so this wasn't possible back then, but now we can improve the situation
(allow specifying names/symbols instead of hashes only).
Unfortunately Go doesn't allow to easily reuse readers in full packages, still
we can have this wrapper with a little overhead (the alternative is to move
specific methods into types of their own, but I'm not sure how it's going to
be accepted user-side).
Notice that int64 types are used for gas per block or registration price
because the price has to fit into the system fee limitation and gas per block
value can't be more than 10 GAS. We use int64 for votes as well in other types
since NEO is limited to 100M.
Some commands don't accept arguments, but users try giving them and don't
notice a mistake. It's a bit more user-friendly to tell the user that there is
something wrong with the way he tries to use the command.
1. Keep initDone check only for the places where cache is directly accessed.
We don't need to check it in other places, otherwise we have a mess of
duplicating checks.
2. Fix bug in code related to block deserialisation. There's no magic, so
checking that initialisation is done is not enough for proper block
deserialisation. We need to manually fill StateRootEnabled field.
3. Since transaction doesn't need network magic to compute its hash, we don't
need to perform Client initialisation before transaction-related requests.
4. Check that cache is initialised before accessing network magic.
5. Refactor the way Policy contract hash is fetched for Client requests.
We don't really need Client initialisation for that, it's OK to fetch Policy
hash on-the-fly.
Unfortunately, testing this code is not possible without an additional wrapper
in `input`, but adding it just to test this seems to be too excessive. Fixes
