* Spit the generated LocalSettings code out during the installer as an aid

* Spit the generated LocalSettings code out during the installer as an aid
  to debugging issues. (Keep this?)
* Use __FILE__ to form path in new LocalSettings.php, so it stays accurate
  when the directory is relocated for typical usage.
* Auto-update $wgCacheEpoch when LocalSettings.php changes on new installs.
  For typical usage this will be a light burden and should reduce confusion
  when the configuration is edited.
* Fix $wgCacheEpoch's effect on client-side caching.