Largefire merge hotfix

This PR fixes the merging issue with Largefire data generation where occasionally the spread history of a smaller fire merged into a larger one is not preserved. And by "fixes", I mean I changed a flag from True to False, which seems to be all that is needed based on our testing. See the diff for more info.

Secondary change, I turned off the flag that invalidates what are perceived to be static flares based on unusually high pixel densities. In practice this sometimes affects actual fires, so it's being turned off for now to avoid any invalidation of events we're actually interested in.