Switch Minification Engine from YUI to CLOSURE

While working on Issues to add deep anchors(MSKINS-167) and Upgrade to Bootstrap 4 (MSKINS-97) the default jsEngine used by minify-maven-plugin raises issues during minify compile's step.

Below the affected js libs:

[bootstrap upgrade]
+ boostrap.bundle-4.4.1.js,
+ jquery-3.4.1.js

[deep anchor features]
+ anchor-4.2.2.js

I managed to modify anchor source file to workaround YUI issue (by replacing opts.class with opts['class'], seems to be a known limitation of YUI https://github.com/yui/yuicompressor/issues/77), but it will be hard to maintain, and definitely not an option for bootstrap upgrade

These problems are fixed by a switch to CLOSURE engine.

Therefore a this improvement seems useful or mandatory for Upgrading Bootstrap to version 4. Also to avoid modification in anchor js lib.