Add the name of the closest previous savegame to charts

As per title.

I mostly, not only due to this game, give some description of what is about to be done in the savegame name. So WHEN you notice an issue with production in the charts, you can hover over a data point and imagine it would pop up the savegame name. E.g. "Start building farms", or "move oil production", ....

How I came about this:
Today I saw my diesel generation was low, 4 years ago in game I saw the drop in the charts. The game up until now was slowly flattening without building for 2000 years. Just the basic and JD's oil processing and research. Today I'm like into the 4 stage of actually building things to expand since everything is flat. But diesel dropped substantially in the last 4 years, but I can't figure out at what building stage this started!
So I figured in stock charts in real life, theres major events posted in the charts, at least that's what I saw pop-up in my mind, only to be throuroughly disapointed that here the charts don't show that :-)

I guess, for now I'll go back to backtracking where it all went wrong :'(

Thanks (for the great game),
AnomynousX