Document the difference local.js and global.js

[tpmccallum]

We used to just have a single secondStateJS.js file.
This search engine can run in two modalities: local and global.
When running in a local single user environment the local.js file (previously known as secondStateJS.js) can be used.
When running in a global multi user environment (served to the world) the global.js file (which talks to the io.py API) can be used.
This must be documented i.e. the index.html file will need to reflect the appropriate js file in the head.

[tpmccallum]

The index file will now stay the same.
We are using a single secondStateJS.js file which can differentiate between local and global mode and choose the appropriate REST call (via JS or via Py Flask)