0514: Activity Stream, fixes #396

AS is out of control. No master switch in FF60+, and in order to 100% sure nothing is collected locally (or external connections made), there are now some 28 prefs (including those coming in FF61). This is re-DICK-ulous. We're not going to bother tracking all that, let alone the labyrinth of code. All users are advised to just make sure they remove the XPI every time they update FF.

user.js

@@ -375,8 +375,11 @@ user_pref("extensions.shield-recipe-client.api_url", "");
  * Just DELETE the XPI file in your System Add-ons directory
  * [1] https://blog.mozilla.org/data/2017/06/05/measuring-search-in-firefox/ ***/
 /* 0514: disable Activity Stream (FF54+)
- * Activity Stream replaces "New Tab" with one based on metadata and browsing behavior,
- * and includes telemetry as well as web content such as snippets and "spotlight"
+ * Activity Stream is the default homepage/newtab, based on metadata and browsing behavior,
+ * and includes telemetry and web content such as snippets, top stories (pocket), top sites, etc.
+ *  - ONE: make sure to set your "home" and "newtab" to about:blank (or use an extension to control them)
+ *  - TWO: DELETE the XPI file in your System Add-ons directory (note this get reinstalled on app updates)
+ * And/or you can try to control the ever-growing, ever-changing "browser.newtabpage.activity-stream.*" prefs
  * [1] https://wiki.mozilla.org/Firefox/Activity_Stream
  * [2] https://www.ghacks.net/2016/02/15/firefox-mockups-show-activity-stream-new-tab-page-and-share-updates/ ***/
 user_pref("browser.newtabpage.activity-stream.enabled", false);