Isolate node_modules inside development container/VM

[richardebeling]

Attempt to fix #1648.

Would be nice if some of you could test it out -- inside the VM, you should have node_modules, but outside, the folder should simply be empty (or have whatever contents you want it to have)

I will have to test around with the setup a bit more, especially trying to make it break when having node_modules populated both inside and outside the VM. In theory, it should work.

We probably also want to document the docker flags used.

[richardebeling]

@niklasmohrin suggested to just use npm's --global flag, but it doesn't work as documented. I've opened an issue with npm. So this is now waiting to see how the issue resolves.

Edit: Seems like the documentation will be removed instead of adding the feature, so we won't be able to use --global mode.

[niklasmohrin]

Works on my machine, although its a bit odd that I still get the empty node_modules on the host machine. Still, this is definitely better than the setup-as-admin we currently have 👍