Multiselect support (#22)

[ajmeese7]

This is a follow-up to #23, with additional functionality and support/integration with os-js/osjs-gui#40.

Currently in a draft state because of the TODO on line 147, which needs the functionality from the MeeseOS commit (the formatStatusMessage function) converted into the various OS.js translations.

I also still need to go back and fix a couple copy/paste eslint errors that I forgot to fix in the first commit :p

[ajmeese7]

I did the best of my ability with the translations, I think everything looks good but I'd definitely like a second opinion because I'm not 100% sure @andersevenrud

EDIT: Whoops, still need to fix the eslint errors real quick, I only focused on the translation messages.

[andersevenrud]

Might not have time to look at this until this weekend.

But at a quick glance things are looking good!

[andersevenrud]

Sorry, but still haven't found time to look at this.

But as I sat here suddenly something dawned on me that we should take a not of.

Most drag and drop handlers are implemented in a way that expects a single object, not an array of objects. So if the goal is to support multiple dnd objects at once this needs a look-in.

[ajmeese7]

When you say "drag and drop handlers" are you referring to the browser API or something else? Because a cursory internet search shows that there are a lot of good ways to handle DnD upload for more than one file simultaneously. There's even an npm package dedicated to this: react-drag-drop-files