Download assets like textures in the content library on demand

The texture assets library can become huge (more than a GB).
Therefore the package should only contain the previews and we should download the actual textures on demand.

The texture should be downloaded before it can be actually added.

Discussion points:

• Should the downloaded texture be stored outside of the project?
  We could download the texture to a shared folder, to avoid multiple downloads.
  This also has the advantage that users behind firewalls etc. can download and install the texture pack directly.

• We have to consider other assets like materials.

• Where to download the textures from and how to maintain this?

Suggesting the following:

We create a new GitLab repo that contains the textures.
Potentially already the zipped version (Does it make sense to compress them?)
Each texture/texture group/package should have its own folder. LFS is enabled of course.
A script uploads every 10 minutes potential changes to our file servers. We have to take into account that syncing to all mirrors can take a few hours.
There is no real protection but each package contains a license file. Once this is implemented Tim is out of the loop.

The installer component would only contain the previews and the "source" should be in the same GitLab repo.

GitLab also provides download links for folders, but this is extremely slow and we might "break" the servers with the load, because
the folder has to be zipped up for each download.

stretch goals:

• We could consider doing texture packs and downloading "packs" of textures at once.

• The previews could also be downloaded, so nothing has to be maintained inside the application package. This makes maintaining and syncing the library easier and more flexible. For the demos/examples, we already do this.