Refactor extension to webpack

This change is the biggest in the history of the project. The entire
project has been refactored so it is built with webpack.

This involves:
- Creating webpack and npm config files.
- Fixing some bugs in the code due to the fact that webpack uses strict
mode.
- Merging some pieces of code which were shared throughout the codebase
(not exhaustive, more work should be done in this direction).
- Splitting the console_inject.js file into separate files (it had 1000+
lines).
- Adapting all the build-related files (Makefile, bash scripts, etc.)
- Changing the docs to explain the new build process.
- Changing the Zuul playbook/roles to adapt to the new build process.

Change-Id: I16476d47825461c3a318b3f1a1eddb06b2df2e89
diff --git a/src/common/contentScriptsUtils.js b/src/common/contentScriptsUtils.js
new file mode 100644
index 0000000..00bc556
--- /dev/null
+++ b/src/common/contentScriptsUtils.js
@@ -0,0 +1,17 @@
+export function injectStylesheet(stylesheetName, attributes = {}) {
+  var link = document.createElement('link');
+  link.setAttribute('rel', 'stylesheet');
+  link.setAttribute('href', stylesheetName);
+  if ('media' in attributes) link.setAttribute('media', attributes['media']);
+  document.head.appendChild(link);
+}
+
+export function injectStyles(css) {
+  injectStylesheet('data:text/css;charset=UTF-8,' + encodeURIComponent(css));
+}
+
+export function injectScript(scriptName) {
+  var script = document.createElement('script');
+  script.src = scriptName;
+  document.head.appendChild(script);
+}