``createClient`` should return the clientID

[lightyear15]

function createClient should return a string with the clientID just created.

[bluele]

Thanks!
Also, in order for the relayer to get a new clientID, it is better to emit an event containing it as well as ibc-go.
https://github.com/cosmos/ibc-go/blob/83315a90626edec5ec876d438c532a48c4e806be/modules/core/keeper/msg_server.go#L44

[bluele]

NOTE: we need to fix this for Connection and Channel as well

[bluele]

Currently, it has already implemented:

• yui-ibc-solidity/contracts/core/25-handler/IBCClientHandler.sol

  Line 38 in d518aaa

  emit GeneratedClientIdentifier(clientId);

• yui-ibc-solidity/contracts/core/25-handler/IBCConnectionHandler.sol

  Line 15 in d518aaa

  event GeneratedConnectionIdentifier(string);

• yui-ibc-solidity/contracts/core/25-handler/IBCChannelHandler.sol

  Line 39 in d518aaa

  emit GeneratedChannelIdentifier(channelId);