Make ckeditor configurable via config (#148)
Before this, ckeditor was configurable by editing the wysiwyg_init.tpl in 2k11/admin. Now, the flow is like this:
 1. wysiwyg_init.tpl is responsible for initializing the editor and the plugins
 2. we provide a htmlare/ckeditor/serendipity_config.js where we specify a sane default configuration, including a small toolbar without harmful elements
 3. if the user wants to overwrite our configuration upgrade-safely, he can do this in htmlare/ckeditor/userconf.js