build: Update 'svgo' to latest v2.8.0 & re-crush images

Updating 'svgo' to v2.8.0 and newest Wikimedia SVG guidelines –
mainly around new whitespace features of SVGO.

Change-Id: I7c9eb84fdaeb50f6ff04c9e5cd2f005e129d555a

package.json

@@ -1,7 +1,7 @@
 {
 	"private": true,
 	"scripts": {
-		"minify-svg": "svgo --config=.svgo.config.js -q -r -f resources/images/",
+		"minify-svg": "svgo --config=.svgo.config.js --quiet --recursive --folder resources/images/",
 		"test": "grunt test"
 	},
 	"devDependencies": {
@@ -12,7 +12,7 @@
 		"grunt-stylelint": "0.17.0",
 		"postcss-less": "6.0.0",
 		"stylelint-config-wikimedia": "0.11.1",
-		"svgo": "2.3.1"
+		"svgo": "2.8.0"
 	},
 	"eslintIgnore": [
 		"lib/**",