Remove loading gif

Instead of an external gif, use the BusyIndicator that exists in the ActionButton.

plugins/Toolbox/resources/images/loading.svg

@@ -1 +0,0 @@
-<svg width="200px" height="200px" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" preserveAspectRatio="xMidYMid" class="lds-rolling" style="animation-play-state: running; animation-delay: 0s; background-image: none; background-position: initial initial; background-repeat: initial initial;"><circle cx="50" cy="50" fill="none" ng-attr-stroke="{{config.color}}" ng-attr-stroke-width="{{config.width}}" ng-attr-r="{{config.radius}}" ng-attr-stroke-dasharray="{{config.dasharray}}" stroke="#0CA9E3" stroke-width="13" r="43" stroke-dasharray="202.63272615654165 69.54424205218055" style="animation-play-state: running; animation-delay: 0s;"><animateTransform attributeName="transform" type="rotate" calcMode="linear" values="0 50 50;360 50 50" keyTimes="0;1" dur="1s" begin="0s" repeatCount="indefinite" style="animation-play-state: running; animation-delay: 0s;"></animateTransform></circle></svg>