Use extracted sensor-applet-interface project

This removes the `src/lab/sensor-applet` folder, the `src/common/mini-class.js` module (which was unused outside that folder), and the `lab.sensor-applet.js` build product from Lab and replaces them with the build product provided by the [sensor applet wrapper project](https://github.com/concord-consortium/lab-sensor-applet-interface) extracted from Lab.

The single sensor model type appears to work. I have not yet checked the dual-sensor model type, nor the 2 projects in the experiments folder that use the updated build product. (And, actually, does the inquiry-space-importer even work now?)