Merge Misbehaviour and Header interface and rename it to ClientMessage

[colin-axner]

Summary

Remove misbehaviour interface and use the Header interface instead (they will have the same functions after #874)

Splitting pr recommendation:

PR 1

Rename proto files of light client misbehaviour. For example, in 07-tendermint, Misbehaviour, should become a DuplicateHeightHeader or something like that.

We should have a normal Header and a duplicate height header. A normal header may update the client if it does not validate BFT time and the duplicate height header may prove a fork resulting in the client becoming frozen.

PR 2

Change the API to use Header instead of Misbehaviour

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[colin-axner]

Let's merge Header and Misbehaviour and name the interface ClientMessage as @AdityaSripal suggests here

[colin-axner]

closed by #1107