Support updating of multiple labels/objects at once

TODO:

[x] transition updateLabel mutation calls to updateLabels and pass in arrays of updates as payload
[x] transition updateObject mutation calls to updateObjects and pass arrays of updates as payload
[x] update upstream dispatched actions in components and middlewares that trigger editLabel (e.g. labelValidated, objectLocked) to support arrays as payloads; update reducers to handle arrays and update image state accordingly
[x] update undo/redo handling
[x] transition createObject and deleteObject to createObjects and deleteObjects (and update animl-api accordingly)
[x] transition createLabel and deleteLabel to createLabels and deleteLabels (and update animl-api accordingly)
[x] update markedEmpty and markedEmptyReverted actions to support marking multiple images as empty at once
[x] update objectRemoved, labelAdded, labelRemoved actions to support multiple objects/labels

tnc-ca-geo / animl-frontend