Migrate from Bower to Yarn

Bower is deprecated since last year and there's also official recommendation to migrate to Yarn [1]. Bower also doesn't support 'shrinkwrap' feature to lock dependencies [2]. Currently, there is no plan to add Bower support into PNC (Project NewCastle - internal Red Hat build system for Middleware, future replacement of MEAD). From the product perspective, we should migrate from deprecated or barely supported tools and dependencies to fully supported and perspective ones.

Most of packages which are available via Bower registry should be also available via NPM registry. If there's a package which is available only via Bower registry and not via NPM registry, it's probably not going to be better maintained (or developed) in future. So it's better to find another one and migrate to it. If it's a Red Hat project we should recommend them to publish their bits to NPM registry.

[1] https://bower.io/blog/2017/how-to-migrate-away-from-bower/
[2] https://github.com/bower/bower/issues/505