fix(cockpit/style): avoid using cleancss compression

This commit improves the following grunt tasks:
 - Windows only, downloads and extracts selenium (and its dependencies)
   without using webdriver-manager
 - sets the "verbose" option of the bower task to "true" to ease
   debugging.
 - re-sets the CSS compression to "compress" instead of "cleancss"

Related to: CAM-1713