Bug 898987 - [bb][refactor] Freeze current BB by moving them into v1 folder

-Moved all BB in shared/style/ to shared/style/v1/
-Moved all BB in shared/style_unstable/ to shared/style/v1/unstable/
-Updated build/webapp-zip.js to reflect those changes and make it more flexible by using this folder structure: style/version/status/ (status folder not required)