N°2847 - Improve SCSS files structure

- Refactor some mixins into helpers
- CSS3 variables set via SCSS variables are now using "interpolation" (#{$my-var} instead of just $my-var) to be compatible with more SCSS compiler
- Overloading some Bulma variables such as font-family

css/backoffice/utils/helpers/_misc.scss

@@ -0,0 +1,46 @@
+/*!
+ * Copyright (C) 2013-2020 Combodo SARL
+ *
+ * This file is part of iTop.
+ *
+ * iTop is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * iTop is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ */
+
+%ibo-centered-content{
+	display: flex;
+	justify-content: center;
+	align-items: center;
+}
+%ibo-text-truncated-with-ellipsis{
+	white-space: nowrap;
+	overflow-x: hidden;
+	text-overflow: ellipsis;
+}
+%ibo-medallion{
+	position: relative;
+	border-radius: var(--ibo-border-radius-full);
+	border: 2px solid var(--ibo-color-grey-300);
+	overflow: hidden;
+	@extend %ibo-centered-content;
+
+	> *{
+		position: absolute;
+		top: 0;
+		left: 0;
+		width: 100%;
+		height: 100%;
+		background-position: center;
+		background-size: contain;
+		background-color: var(--ibo-color-grey-500);
+	}
+}