Add replay function

[elecnix]

Add a button to trigger the dashboard to flush its data and request a replay of all events from the collector, but at a defined rate.

Currently, the replay happens one device at a time, but that needs to change to sending events from all devices in the same time sequence they were published (devices interleaved).

The dashboard should tell the collector how much to compress or expand time. A ratio of 2 should mean a replay rate of 2X, twice as fast as the original events. A ratio of 0.5 should mean twice as slow.

Since the dashboard flushes all its data, and does not store snapshots, it should also ask the collector to apply the replay ratio only starting at a given timestamp. This way, we can replay a day of interest without having to wait for the whole season to happen :)