Timeline: Issue with axis formatting between dynamic instances

[cwewells]

I've noticed an issue with multiple instances of the Timeline control. I've created new instances of the control in ES6 classes, with one changing the axis format. After destroying the instance, and creating a new vis.timeline in another class, the axis formatting function still fires from the old instance (even with supplying a new Options object).

I have been able to work around this by explicitly creating a formatter for both instances, even though one does not change the default formatting.

Would be nice if the axis formatting can revert to the default when destroying an instance, so that custom formatting is explicitly set and does not "travel" across instances.

Ciao