Use CaveView.js as a window into the survex data

[goatchurchprime]

There's a .3d viewer code that runs in the browser that has an API
https://aardgoose.github.io/CaveView.js/reference.html

If we have hooks on the expo-server that recalculates the .3d files as soon as there is a commit to the data, we could use this in place of aven so that you'd only need some links on the page to load up the correct cave section in the correct orientation and settings. No more looking for obscure files in the directory structure and command line running cavern/aven, when you could go there straight away.

We are after adding in features such as highlighting all the QMs (question marks) and their descriptions of how good/crappy they are.

[PhilipSargent]

CaveView is currently working beautifully on the refreshed server (Debian 10 buster) but Wookey was wondering whether we should have an updated version.

[PhilipSargent]

troggle now puts the .3d file in the same folder as the .svx file, so file clashes that happened between .3d files won't happen again. So we can re-enable CaveView.