* Add `Clone.prototype.getCostumeIndexByName`, keep in range
* Add basic costume primitives from Scratch 2.0
* Add costume getter block
* Add properties and methods for distinguishing stage and sprites-vs-clones
* Add backdrop-related looks blocks
* Fix up "switch to backdrop" to be working
* Costume/backdrop reporters are 1-indexed
* Fire "when backdrop switched" hats
* Cut cloning helpers for a separate PR
* Disable many blocks on the stage
* Refactor into _setCostumeOrBackdrop; implement switch backdrop and wait
* Fire hats even when backdrop unchanged
* Fix SB2 variable imports!
* Fix expectedArg field types
* motion_pointindirection uses math_angle
* Fix "think for secs" expected input
* Add handling for empty input case (empty if-else, for example)
* Fix opcodes for if_else, repeat_until, set tempo
* Specialized number fields for SB2 import
* Convert color picker numbers to hex in SB2 import
* KEY_OPTIONS -> KEY_OPTION
* Backdrop blocks get BACKDROP
* Update toolbox XML to match naming changes
* Merge in math_angle case
* Move color converter to its own utility
* Fix merge conflicts
* Add negative color check.
* Fix keyoptions naming
* Pen JSON tweak post-scratch-blocks update
* Always add `next` to block representation
* Add `shadow` property to inputs, to maintain obscured shadows
* Create obscured shadows in SB2 import
* Add XML import of obscured shadows
* Alias SB2 shadow inputs to block inputs
* Add shadow to inputs on "delete inputs" test
* Add a small test to ensure obscured shadows are preserved
* Add more obscured shadow tests
