Upgrade most dependencies

In addition to general upgrades, css-loader, file-loader, and
mini-css-extract-plugin had major upgrades that were manually tested
one by one.

package.json

@@ -53,15 +53,15 @@
     "@types/tmp": "^0.1.0",
     "awesome-typescript-loader": "^5.0.0",
     "bootstrap": "^3.3.7",
-    "css-loader": "^2.1.0",
+    "css-loader": "^3.0.0",
     "cssnano": "^4.0.5",
-    "file-loader": "^3.0.1",
+    "file-loader": "^4.0.0",
     "hls.js": "^0.12.2",
     "html-loader": "^0.5.1",
     "html-webpack-plugin": "^3.0.6",
     "less": "^3.9.0",
     "less-loader": "^5.0.0",
-    "mini-css-extract-plugin": "^0.6.0",
+    "mini-css-extract-plugin": "^0.7.0",
     "postcss-loader": "^3.0.0",
     "react": "^16.1.0",
     "react-dom": "^16.1.0",