Structure of cloud.json:

* The file is an array of objects.
* Each object represents a floor. For example, the 1st floor is represented by .[1]
* Each floor object contains one or more corridor arrays. For example, the 2nd corridor on the right on the 4th floor is represented by .[1]["-2"]
* Each corridor array contains one or more chest elements. They are item stubs with the following additional optional keys:

* name: a string specifying the name to be shown on the sign, if different from the item name.
* sorter: a number representing the x coordinate of the pre-sorter, for stackable items on floors 5 and 6.