Disable user comment counts...
Added caching ability to Gdn_Theme::Module().
Cache non-existent users as NULL to avoid hitting the db on subsequent requests.
Merge branch 'master' into feature/mega-opt
Revert "Disable user comment counts..."

This reverts commit 6dcdf6b7914885f7f3741ef9ea2dcb90ca3250b7.
Merge branch 'master' into feature/mega-opt
Refactor the newing up of the PDO connection so that other PDO connections can be created with the database settings.
Implemented master/slave database functionality.
- Added Gdn_Model->Options().
- Added an $Options parameter to Gdn_Model->GetID().
Added the $Options parameter to DiscussionModel->GetID() and CommentModel->GetID().
Make sure not to select from the slave after saving a comment/discussion.
Merge branch 'master' into feature/mega-opt
Merge branch 'master' into feature/mega-opt
Run the update comment count on the master when posting via api.
Potentially improve handling of persistent cache connections.
Fix typo in variable usage for GDN_Memcached.
Allow selective disabling of APC preaching.
CommentModel: Don't recalculate category comment counts every single comment post.
Only query the current subtree of a category.
- Setup indexes for the categories archive.
- Remove the plain Discussion.CategoryID index because either of the other two category indexes will suffice.