Process images with Webpack

This adds a `file-loader` rule to the Webpack build so that any requests for
image resource will be output into the app's output directory, but with an extra
content has appended so that we can safely use a long cache lifetime.

The CSS and SCSS rules are also changed to use `css-loader` so that any `url`
inside is automatically processed by the new image rule above.

package.json

@@ -33,8 +33,8 @@
     "build:res": "node scripts/copy-res.js",
     "build:modernizr": "modernizr -c .modernizr.json -d src/vector/modernizr.js",
     "build:compile": "npm run reskindex && babel --source-maps -d lib src",
-    "build:bundle": "cross-env NODE_ENV=production webpack-cli -p --progress --bail --mode production",
-    "build:bundle:dev": "webpack-cli --progress --bail --mode development",
+    "build:bundle": "cross-env NODE_ENV=production webpack -p --progress --bail --mode production",
+    "build:bundle:dev": "webpack --progress --bail --mode development",
     "build:electron": "npm run clean && npm run build && npm run install:electron && build -wml --ia32 --x64",
     "build:react-sdk": "node scripts/npm-sub.js matrix-react-sdk run build",
     "build:js-sdk": "node scripts/npm-sub.js matrix-js-sdk run start:init",
@@ -100,6 +100,7 @@
     "concurrently": "^4.0.1",
     "cpx": "^1.3.2",
     "cross-env": "^4.0.0",
+    "css-loader": "^2.1.0",
     "electron-builder": "^20.29.0",
     "electron-builder-squirrel-windows": "^11.6.1",
     "electron-devtools-installer": "^2.2.4",
@@ -110,6 +111,7 @@
     "eslint-plugin-flowtype": "^2.50.3",
     "eslint-plugin-react": "^7.11.1",
     "expect": "^1.16.0",
+    "file-loader": "^3.0.1",
     "fs-extra": "^0.30.0",
     "html-webpack-plugin": "^3.2.0",
     "json-loader": "^0.5.3",
@@ -136,7 +138,6 @@
     "postcss-scss": "^1.0.6",
     "postcss-simple-vars": "^4.1.0",
     "postcss-strip-inline-comments": "^0.1.5",
-    "raw-loader": "^0.5.1",
     "react-addons-perf": "^15.4.0",
     "react-addons-test-utils": "^15.6.0",
     "rimraf": "^2.4.3",