Renaming of extensions/chrome folder to extensions/chromium, and small tweak to manifest.json description as per #3600
adjusted paths in make.js to reflect chromium instead of chrome
adjusted some more chrome references in make.js and README.js as per @yurydelendik's suggestion
Merge pull request #3602 from operasoftware/master

Make Chrome extension vendor-neutral
Fixes 'make web' after chromium directory remaning