Merge pull request #241 from stuartrowe:ui-refresh
* Replace icons with symbols to match Jenkins UI
* Fix symbol dimensions
* Add outline versions of new symbols
* Use outline symbols
* Make the original filled symbols thinner
* Minify symbol svgs
* Revert back to original filled symbols
* Use pricetag-outline for TagAction icon
* Change P4Hook symbol to P4 (product) Logo