Add option to clear localstorage

[akoeplinger]

I think I hit an issue where something was cached wrongly and had to clear localstorage. would be nice to have a button in the viewer for that.

[xmcclure]

Can you describe what the bad cache data looked like?

[akoeplinger]

It showed build XY as having a failure, but when I opened it on Jenkins it was actually a green build. I didn't look into it too much, but clearing localstorage fixed it.