Timeline: events may overlap at the highest zoom level when they share the same or similar date

[jimsafley]

See this post.

The default TimelineJS zoom_sequence needs to be modified to accommodate many events that share the same or similar date. So, in Mapping\Site\BlockLayout\AbstractMap::getTimelineOptions(), adding

'zoom_sequence' => [0.5, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 200, 500, 1000],

to the array may provide enough zoom levels.

We may consider making this configurable by the user, but I'm leaning toward just hard-coding the sequence above. Another consideration is that the higher the sequence number, the more load on the browser, to a point of temporarily slowing it to a crawl. 1000 is slow. Anything higher than 1000 risked crashing my browser.