Bump base version for Chrome and Firefox addons

Give both addons the same base version, which
is higher than the minor for either published version.

The version is lower than the command-line app to reflect
that the extensions are less mature.
Setup automatic deployment of Chrome extension

Use the Chrome Web Store API to automatically publish commits
to the master branch to the Chrome Web Store.
Fix Chrome extension zip build failure if there was no pre-existing Zip file

Add force option to 'rm' in case package.zip does not already exist
and quieten output from Chrome extension build.
Make the publish-chrome-extension.js utility script reusable for other apps

Get the Chrome extension Zip file path, app ID and client ID from
the command line and env vars respectively rather than hardcoding
them into the script.

This makes the script re-usable for other extensions in future.