Add Wiki entry for how the application handles IBC MsgTransfer, MsgAck and MsgRecvPacket as sends/receives

[pharr117]

We have been message type ignoring MsgTransfer. This is due to the following commit:

279283f

The original idea was to only index MsgAcks, so that we would not have a double send value:

1. MsgTransfer -> ignored
2. MsgAck -> indexed as a send

Some users have questioned why MsgTransfer transactions are not being indexed and we should dig into this behavior a bit more and see if the logic is correct.

[pharr117]

We will be adding a wiki entry to explain how the application indexes IBC messages as sends/receives