Some layout fixes and adding possibility to work if Zikula is installed in a subdirectory.

This PR is necessary too if you want to get it work in a subdirectory: https://github.com/zikula-modules/Scribite/pull/92

Changes:
- Some layout fixes.
- Smarty plugins are now located in the plugins folder.
- Moved files to root for easier developement.
- Made it working if Zikula is installed in a subdirectory.
  ***Notice:*** To made it working I needed to change a few lines of Kcfinder code (See #3). If you don't like changes in vendor code, it might be possible to close #3 and instead add a hint in the README file.