Added number of stalls to supercharger and a number of other small tweaks

- Added number of stalls to superchargers.txt
- Added Stalls to the detail popup on map and to the data table. ***untested***
- Added script that reads superchargers.txt for teslamotors.com/supercharger pages. The script crawls those pages to determine stall numbers for each supercharger.
- build.sh checks for OS type for nodejs command.
- fixed a minor typo in FieldDefinition.js and SiteTransform.js