Implement the actual ICS20 protocol

[DariuszDepta]

I guess, you are using a simplified version of the actual ICS-20 protocol here, but I do want to note that this is not how the denom works in the actual protocol. We will have to make changes to this if we want to implement IBC Callbacks later down the road.
Here's a quick example of how it looks on chain:
If I send ujuno from Juno to Osmosis, the denom is ujuno. If I send it back from Osmosis to Juno, it is transfer/channel-42/ujuno.
According to the spec, it's formatted as {ics20Port}/{ics20Channel}/{denom} using the source port and channel (so the ones on Osmosis in my example). To detect that, we would need to check for that prefix and remove it to get the denom on the receiving chain.
Side note: On most chains this denom is also different than what is shown to the bank module because it gets hashed with Sha256 and prefixed with ibc/

Originally posted by @chipshort in #184 (comment)