Activity: Delegate statistics: Delegates name is not shown instead of id

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Steps to reproduce

1. Go to the delegate's acc with votes from named account, (devnet: 17110047919889272525L)
2. Open Delegate statistics in Activity
3. Look at Who voted

Actual behaviour

Delegate's id
(devnet: 4401082358022424760L )

Expected behaviour

Delegate's name

child of #812

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Investigation results:
The problem is that in the 0.9.X API, the vote and voter objects contained username, but in 1.0.0 this field was removed.
So there is no easy way to display the delegate name. Next, I will look into non-easy ways.

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So the best solution is to use lisk-explorer as a data source for this, but that involves a lot of extra changes. E.g. being able to set explorer node when setting a custom node, setting up our Jenkins to run explorer node etc. So it won't be done in 1.0.0

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Cleaning up - Closing issues that were open for a long time without any update. We can re-open if needed.