Moved Navigation Bar Functionality to use the New Tree

Notable differences:

* For an external module in file `a/b/c.ts`, the "top-level" container is displayed as `"c"`.
why does this function exist...
```
 export function getModuleNameFromFilename(filename: string) {
    return removeFileExtension(filename);
}
```

just us removeFileExtension, I do not see the point of a wrapper.