Added eslint. To lint, npm run lint.

Linted the entire project. Using different rules for the script files
as there are a lot of undefined variables just because of the way the
DOM's global scope works.

Mostly just code cleanup, however the linter did catch a minor bug with
a settings regex. That has been corrected.

package.json

@@ -12,7 +12,8 @@
     "dist:win": "npm run dist -- --win --x64",
     "dist:mac": "npm run dist -- --mac",
     "dist:linux": "npm run dist -- --linux --x64",
-    "dist:all": "npm run dist -- -wl --x64"
+    "dist:all": "npm run dist -- -wl --x64",
+    "lint": "eslint --config .eslintrc.json --ignore-pattern app/assets/js/scripts/*.js . && eslint --config .eslintrc.scripts.json app/assets/js/scripts"
   },
   "engines": {
     "node": "10.5.x"
@@ -47,7 +48,8 @@
   },
   "devDependencies": {
     "electron": "^2.0.5",
-    "electron-builder": "^20.24.4"
+    "electron-builder": "^20.24.4",
+    "eslint": "^5.2.0"
   },
   "build": {
     "appId": "westeroscraftlauncher",