Provide AerialCloseAll and AerialCloseAllButCurrent commands

[krishnakumarg1984]

Description
Let's say we are editing two related files in a project as vertical splits. We have configured aerial such that each of them have their corresponding aerial window open i.e. there are a total of 2 aerial windows on screen.

One way to quickly focus on the screen might be to close all the symbols outline windows and just focus on the actual file contents. In this scenario, having an :AerialCloseAll command can be helpful to quickly close multiple aerial windows down. A counterpart, :AerialOpenAll will then help to restore the previously open aerial windows.

Now, here is another scenario I faced.

1. Editing one file heavy on symbols with its aerial window open
2. Editing other splits with moderate amount of symbols with their aerial windows open

(e.g. a lengthy C++ source file and three moderate-length included headers).

It is helpful to have just the symbols of the current buffer to be quickly visible, and all other symbols tree closed down (while still having those other buffers remaining open for referring). In this scenario, having a :AerialCloseAllButCurrent command shall be handy.

[stevearc]

Commands added!

[krishnakumarg1984]

Superb. Works well. Thank you for considering this.