Remove JavaScript link insertion code

* Since change I92dac7589, the shop link insertion is done in PHP.
  The JavaScript code was retained as a fall-back for pages that were
  cached before the update. But since then nearly two months have elapsed.
* Removed WikimediaShopLinkHooks in favor of a single anonymous function.
* Removed $wgWikimediaShopEnableLink config var. Since inserting the link is
  the sole feature of this extension, $wgWikimediaShopEnableLink is basically
  $wmgUseWikimediaShopLink by another name.
* Bump version to 1.0, which reflects the fact that the extension is considered
  complete.

Change-Id: I667e169c0fd25eafbffee8bbb7e58a9c7a6cd6c7
Merge "Remove JavaScript link insertion code"