Add infrastructure

Add several tools to help with the extension development:

- Add .editorconfig file to set formatting options for the code editors.
- Add generateManifest.bash to generate the manifest.json file
  dynamically, from a template at templates/manifest.gjson. The
  manifest.gjson file can have lines defining what parts of the manifest
  are added for each target browser.
- Add release.bash to generate the extension ZIP files.
- Add Makefile to serve as a wrapper for the release.bash script.
- Add tagRelease.bash to help tag versions in Git accordingly.
- Add docs to explain all this new infrastructure (will need to be
  updated in the future with more details).

Change-Id: I698ffc59d0d2ec02b483935f7860e95760951a42
diff --git a/templates/manifest.gjson b/templates/manifest.gjson
new file mode 100644
index 0000000..5889bf3
--- /dev/null
+++ b/templates/manifest.gjson
@@ -0,0 +1,29 @@
+{
+  "manifest_version": 2,
+  "name": "__MSG_appName__",
+  "description": "__MSG_appDescription__",
+  "version": "0",
+  "version_name": "dirty",
+  "permissions": [
+    "contextMenus",
+    "storage",
+    "notifications"
+  ],
+  "icons": {
+    "16": "icons/translate-16.png",
+    "32": "icons/translate-32.png",
+    "64": "icons/translate-64.png",
+    "128": "icons/translate-128.png",
+    "256": "icons/translate-256.png"
+  },
+  "background": {
+    "scripts": ["background.js"],
+    "persistent": false
+  },
+  "options_page": "options.html",
+  "options_ui": {
+    "page": "options.html",
+    "chrome_style": true
+  },
+  "default_locale": "en"
+}