#125 toggle to only show open files in treebrowser

treebrowser (6)

A toggle button in the toolbar of the treebrowser which will limit the display of files and folders to only those related to currently open files.

This would make it easier to navigate between active files when there are perhaps 10-20 files open but they are in different directories and there are many directories and files in the project.
It would also help when navigating between files with the same name but different directories.

If I had this feature toggled on and I wanted to open another file, I would toggle the button off, the directory listing would reinitialize focused on the current active file, I would open the new file, then toggle the feature back on.

When this feature is off, it would be helpful to have indication, perhaps text color, of whether a particular file is currently open (green or bold?) or unsaved (red).
This would follow the existing functionality of the open tab where the filename is displayed in red to indicate that the file has unsaved changes.