Nodes generate and publish the FBOs they need, unless available already.

[emanuele3d]

If node A needs FBO F, it should first check if it exists already. If not, it should generate it and publish it so that other nodes can find it.

This feature will rely on string identifiers and FBOs with hardcoded characteristics. Eventually, in a different issue, we might want to switch to generating, publishing and finding FBOs according to their characteristics rather than their identifiers or in conjunction with their identifier.