Image action toolbar

[nathanielrindlaub]

Progress towards https://github.com/tnc-ca-geo/animl-frontend/issues/41

Controls to add:

• [ ] undo / redo
• [x] validate all / invalidate all objects
• [x] edit all labels (toggle open category selector)
• [x] add object
• [x] mark empty (depends a bit on where we land with #77)
• [x] repeat last action (i.e., if you labeled the last image with a fox, apply fox to this object)
• [x] unlock all (no need for lock all; locking should always be a side-effect of validation)

[nathanielrindlaub]

Style/UX considerations:

• [x] prevent actions from being taken on locked objects
• [x] hide category selector if user clicks out of it
• [ ] collapse buttons to just icons when toolbar is narrow
• [x] add tooltips
• [x] make sure nothing strange happens when image is large (e.g., filters panel is closed)

[nathanielrindlaub]

• [ ] add "remove mark empty"?