Merge pull request #2124 from vanilla/hotfix/memcached-defaults

Updated config defaults to include sane defaults for memcached
Fix bug in DiscussionModel->SetField() when called with an array.
Use the .Hidden class on the preview button instead of jQuery’s hide/show methods.

This is so that the write button can be styled with display: inline-block. Otherwise it gets set to display: inline when shown.
Merge pull request #2132 from vanilla/hotfix/comment-preview-hide-show

Use the .Hidden class on the preview button instead of jQuery’s hide/show methods.
Merge pull request #2131 from vanilla/hotfix/discussion-setfield-fix

Fix bug in DiscussionModel->SetField() when called with an array.
Place memcached defaults in memcached wrapper instead of config-defaults