Port over minimum required LESS variables from MobileFrontend

From now on Minerva will maintain its own variables outside
MobileFrontend.

Bug: T171016
Change-Id: I05430963cc2fb66b50c063bc8e95621abcbbbea1

minerva.less/minerva.mixins.less

@@ -1,5 +1,5 @@
-@import 'mobile.variables';
 @import 'mediawiki.mixins.less';
+@import 'minerva.variables.less';
 @import 'mediawiki.mixins.animation.less';
 
 // Generic mixin for applying styles to text that accompanies/adds context to workflows

minerva.less/minerva.variables.less

@@ -1,6 +1,22 @@
 @import 'mediawiki.ui/variables';
-// FIXME: Remove this dependency. Should not depend on mobile.variables
-@import 'mobile.variables.less';
+
+@z-indexBase: 0;
+@z-indexOverOverlay: 2;
+
+@fontFamily: 'Helvetica Neue', 'Helvetica', 'Nimbus Sans L', 'Arial', 'Liberation Sans', sans-serif;
+@tocFontSize: 0.8em;
+
+@indicatorFontSize: 0.4em;
+
+// colors
+@grayMediumLight: @colorGray10;
+@grayMediumDark: @colorGray5;
+@grayMedium: @colorGray7;
+@grayLight: @colorGray12;
+@grayLightest: @colorGray14;
+
+@wgMFDeviceWidthMobileSmall: 320px;
+@wgMFDeviceWidthDesktop: 1000px;
 
 @skinContentBgColor: #fff;
 

skinStyles/mobile.pointerOverlay/minerva.less

@@ -1,5 +1,7 @@
 @import 'minerva.variables';
 
+@colorTutorial: #2e76ff;
+
 @media all and ( min-width: @deviceWidthTablet ) {
 	// Take into account padding in width of pointer overlay so that it
 	// can point to anything in the containing content area and avoid