Plugin template: i18next namespace hard-codes plugin name

When we added react-i18next to the console plugin template, we hard-coded the plugin name many places in the code. This manes that it's difficult to change the plugin name when using the template – something we expect everyone to do. The plugin docs that describe how to change the name are out of date and don't work now due to this change.

I'm not sure we should have i18n enabled by default since it makes creating a simple plugin difficult, and I expect few customers writing plugins to use this. It might be better on a separate branch that those who want i18n can include. (Or better we can write an npx command like npx create-react-app that prompts you, but that is out of the scope for this defect.)