Add option to cache previously expanded/collapsed folders

[daedsidog]

I have a large project which I constantly have to expand every time I start work. What I did before was just expand the root folder which recursively expanded all the project's folders, but since my project has grown this is no longer efficient as there are folders that contain many files which I do not want expanded, so I have to expand the folders I want every time I start the explorer which consumes a lot of time.