Enhancements for Code Explorer panel

[pjj]

I've been using Code Explorer panel mostly to look at my TODOs, but I'd love to use it more. There are some shortcomings, though, so I ask you to kindly consider these points:

1) Seems like not all files need to display the CE elements (I mean Module/TODO/Favorites), this is the case with text files*) -- please add "not applicable" message into the upper field (but see point 4 below).

*) If I change highlighter for a text file to "Markdown", CE elements appear after a while -- but TODOs are not recognized.

2) For the files that will have its code analyzed -- please add a spinner, so a user would know it is going to be shown eventually (this happened many times for me, that CE elements appeared only after a while).

3) Please make it possible to reorder CE elements OR allow to set one of these as a default: I don't care about the display order, but since I'm interested in TODO list more than in Modules nor Favorites, after switching to another tab I need to click on TODO line again.

4) Please add Bookmarks as the 4th CE element to complement the other three (yes, I know there's Search > Find Bookmark; yet there's Search > Find Notes/TODO too).

Edit: There's a separate Bookmarks panel... I guess please disregard my 4th point.

There are a couple of bugs in there and I will report them in another board.