Add auto-reload/refresh support for Chrome extension

# Experimental

This branch/PR adds auto-reload/refresh support for the Chrome extension.

Researched + investigated many ideas and options.  Took inspiration from http://livejs.com/

This totally works, but is incomplete in multiple ways:

1. The additional code in `manifest.json` needs to be limited to development builds.
1. The `[grunt-]crx` changes are theoretically off-topic now, as they turned out to be unnecessary in the end.
1. The added code and documentation contains `@todos`

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This is a public feature branch to enable collaboration + PRs.  Do not rebase this branch; only add commits (or ideally merge PRs against it).