Key bindings arrays for and some visualisation viewer function

[bdamay]

Hi guys, First of all i would like to thank you for the amazing job you're making with this new bimsurfer. I don't know if you're opened to pull requests, but you might though consider taking a look at this one.

Basically 2 proposals for viewer.js: First, 1 array of actions that is passed to the canvas eventListener ans avoiding some if(e.key==='...' else if ...). Each action is taking a viewer method to trigger on given keypressed. Second, i made some method for the viewer at the end of the file (like inverting visibillity, hiding unselected objects etc..)

Let me know if this kind of stuff may be of some interest to you or if not. Happy Christmas