Build: Fix i18n validation concat task

Fixes #3527
i18n: First pass at filtering out unused strings
Merge pull request #3528 from nschonni/v4-fix-i18n-concat-task

Build: Fix i18n validation concat task
Merge pull request #3529 from pjackson28/slimi18nbase

i18n: First pass at filtering out unused strings from base.js (v4.0)
Demos: Generate Working examples from meta data