Patch events data storage should be refactored to include historical events

[hhyyrylainen]

so that they can be correctly displayed in the auto-evo exploring tool as swapping generations doesn't work correctly now

I did already request some changes to the code so the API interfaces to the rest of the code should be mostly done to support the patch event list to be persistent and storing the event times (instead of the current way that it is a list of just current events that gets cleared each time).

I think this would need to be done in time for 0.8.0 as otherwise the save data format for the events would end up changing.

[hhyyrylainen]

I tagged this as easy as it should be pretty easy to just convert the events to either have the times in them or to make a dictionary of lists like the timeline events are (where the key is the time, though that might be a bit hard to do if we allow events that last multiple generations).