Switch to using attribute names for object names in nodebotui json

This simplifies our code and allows for easier growth moving forward.

I've also added a simple static file server to demoserver.js

I've also switched from 
````data-thresholds="inMin, inMax, outMin, outMax"````
to
````data-thresholds="inMin, inMax" min="outMin" max="outMax"```` 
since those attributes already exist in the HTML spec and control range input types.

Addresses issues #15 and #19