Start to work on a better UX for codevis

There are many things in the current UX that came directly from the old code port, but this makes no sense anymore. This code removes some concepts such as:

1 - Multiple, Different, ways to load a graph, with hard to follow code-paths. 2 - the MainNode entity, that's supposed to be the node we are looking at now. The problem is that this was also used as a hint to the GraphLoader, and misused as "selection' in some cases.