Add handles to playlist sort tracks

[ofsound]

Fixes #764

I used CSS to change what can be clicked on within a track asset, and to change out the graphics for our new handles.

Bugs

• Something is up with Safari, not sure if it's related to the handles, but I get only every other drag attempt to work! — looks like it's that you can't re-drag on Safari 13, bug is here: Safari 13 loses drag event SortableJS/Sortable#1571
• FF and Chrome on MacOS appear happy over here
• Mobile Chrome and Safari, the handles and dragging appear to work fine, but the ghosts and final sorting I'm not sure are working!
• confirm reorder spec is happy

Open needs

• Handles need to show up on percy and aren't yet
• green checkmark shows up next to "saved" on percy
• Add mini-handle svg into the instructions and edit it to read "Reorder your playlist by dragging your tracks by the ||| icon. Remove them from the playlist with the X icon."

[sudara]

It turns out the playlist reordering spec was working on master https://percy.io/alonetone/alonetone/builds/2671620

However there was no flash alert...

[sudara]

@ofsound I think this just needs another round of QAtune and that mini icon put into place...