Refactor generateManifest infra tool

- Changed from using bash/perl to using go.
- Now "if" statements in .gjson files can be stacked, and there can be
  conditional "or" statements inside, like |#if defined(A || B)|.
- Go tests were added to make sure that the generateManifest tool
  continues to work as expected.
- Updated docs to reflect the fact that the manifest is now generated
  with a different tool, and Go is now required in the build phase.

Change-Id: Id866d1a49a7ab4aac2dcf8d188c56bb8254a80de
diff --git a/testdata/manifest_frozen.gjson b/testdata/manifest_frozen.gjson
new file mode 100644
index 0000000..8d93b2e
--- /dev/null
+++ b/testdata/manifest_frozen.gjson
@@ -0,0 +1,89 @@
+{
+  "manifest_version": 2,
+  "name": "__MSG_appName__",
+  "version": "0",
+#if defined(CHROMIUM)
+  "version_name": "dirty",
+#endif
+  "description": "__MSG_appDescription__",
+  "icons": {
+    "512": "icons/512.png",
+    "128": "icons/128.png"
+  },
+  "content_scripts": [
+    {
+      "matches": ["https://support.google.com/s/community*"],
+      "js": ["common/content_scripts.js", "content_scripts/console_inject.js"]
+    },
+    {
+      "matches": ["https://support.google.com/s/community*"],
+      "js": ["common/content_scripts.js", "content_scripts/console_inject_start.js"],
+      "css": ["common/console.css"],
+      "run_at": "document_start"
+    },
+    {
+      "matches": ["https://support.google.com/*/threads*"],
+      "js": ["content_scripts/forum_inject.js"]
+    },
+    {
+      "matches": ["https://support.google.com/*/thread/*"],
+      "exclude_matches": ["https://support.google.com/s/community*", "https://support.google.com/*/thread/new*"],
+      "js": ["common/content_scripts.js", "content_scripts/thread_inject.js"],
+      "run_at": "document_end"
+    },
+    {
+      "matches": ["https://support.google.com/s/community*", "https://support.google.com/*/thread/*"],
+      "exclude_matches": ["https://support.google.com/*/thread/new*"],
+      "js": ["common/content_scripts.js", "common/cs_event_listener.js", "content_scripts/profileindicator_inject.js"]
+    },
+    {
+      "matches": ["https://support.google.com/*/profile/*"],
+      "js": ["common/content_scripts.js", "content_scripts/profile_inject.js"],
+      "css": ["common/forum.css"]
+    }
+  ],
+  "permissions": [
+    "https://support.google.com/s/community*",
+    "https://support.google.com/*/threads*",
+    "https://support.google.com/*/thread/*",
+    "storage"
+  ],
+  "web_accessible_resources": [
+    "injections/profileindicator_inject.js",
+    "injections/profileindicator_inject.css",
+    "injections/ccdarktheme.css",
+    "injections/batchlock_inject.js"
+  ],
+  "browser_action": {},
+#if defined(CHROMIUM)
+  "options_page": "options.html",
+#endif
+  "options_ui": {
+    "page": "options.html",
+#if defined(CHROMIUM)
+    "chrome_style": true,
+#endif
+#if defined(GECKO)
+    "browser_style": true,
+#endif
+    "open_in_tab": false
+  },
+  "background": {
+#if defined(CHROMIUM)
+    "persistent": false,
+#endif
+    "scripts": [
+      "common/common.js",
+      "background.js"
+    ]
+  },
+#if defined(GECKO)
+  "browser_specific_settings": {
+    "gecko": {
+      "id": "twpowertools@avm99963.com",
+      "strict_min_version": "57.0"
+    }
+  },
+#endif
+  "default_locale": "en"
+}