Minor improvements for Operations page

[bakarapara]

I suggest to

1. Change order in Slashed Tokens section to show newest events at the top of the list.
2. Add filter to show only Slashed events that affected balance

Otherwise user needs to scroll the page to the bottom to see if anything changed.

[Shadowfiend]

Thanks! We'll poke at this and make sure there wasn't a particular reason it was implemented the current way.