Remove bootstrap import from mixins

Similar to last release

Remove bootstrap-sass

We've removed bootstrap-sass since it is not a dependency.

More base styles

• Move panels and buttons base styling from www
• Move background.scss specific styles from core.scss

Adjust Table Header Colors

• The table header colors are too light to read. They have been adjusted.

Exctract kununu-icons

Extract the kununu-icons so that they must not be included.

Update paths for node_module

This theme uses npm for it's dependencies (bootstrap/fontawesome)