GUI: Added ESLint to gulp tasks
GUI: Linted files
Fixed an error in the build script

JIRA-TASKS: ONOS-6522, ONOS-6521

Change-Id: Ie72abfe6cbe21c8946f219be6193344b67ec6dd1
diff --git a/tools/gui/package.json b/tools/gui/package.json
index 4c2aeb0..a6a79f2 100644
--- a/tools/gui/package.json
+++ b/tools/gui/package.json
@@ -14,11 +14,18 @@
     "babel": "^6.23.0",
     "babel-core": "^6.25.0",
     "babel-preset-es2015": "^6.24.1",
+    "browser-sync": "^2.18.12",
+    "eslint": "^4.2.0",
+    "eslint-config-google": "^0.9.1",
     "gulp": "^3.9.1",
     "gulp-concat": "^2.6.1",
+    "gulp-eslint": "3.0.1",
+    "gulp-if": "^2.0.2",
     "gulp-sourcemaps": "^2.6.0",
     "gulp-strip-comments": "^2.4.5",
     "gulp-uglify": "^3.0.0",
+    "gulp-webserver": "^0.9.1",
+    "http-proxy-middleware": "^0.17.4",
     "jasmine-core": "^2.6.4",
     "karma": "^1.7.0",
     "karma-babel-preprocessor": "^6.0.1",