Feature request: Recenter model

[KenLucke]

I accidentally did a two finger swipe while over the visualizer, and the build plate and model went zooming off somewhere into the nether regions of the space-time continuum (I presume that Eddie's there, too*). No way to find where it was and return it into the view. I had to reload (not reboot) the OP instance to get it to return to the default.

A "maintain maximum size view"option would be nice, too, that would constantly make sure that the entire model is zoomed in as close as possible.

[*Obligatory HHGTTG reference.]

[Kragrathea]

I'd like to keep buttons and options to a minimum for simplicity sake. I might add a "reload gcode" button that would also recenter the view, but it wouldn't be that much different from just refreshing the page.

[Kragrathea]

I am coming around to adding a reset camera button somewhere.