* Import lists and variables from SB2
* Switch to Variable and List objects
* Add Clone.lookupOrCreateVariable, Clone.getVariable, Clone.setVariable
* Add (get, set, change) variable blocks.
* Copy variables and lists on clone instantiation
* Move variable options closer to blocks
* Add list primitives
* Move variable and lists storage to `Target` instead of `Clone`
* Move _computeIndex to a Cast function
* Rename `getList` -> `getListAsString`
* Renames renames
* Remove extra check in Cast.isNaN
