Convert all addStyleSheet() to addStyleSheetVersion() and addScript() to addScriptVersion() of the administrator templates
Fix JFactory::getApplication() typos
Mediatag improvements

- Use the database to store and retrieve the media tag, in stead of the users session
- variable === null in stead of isnull() for small performance improvement
- Some other minor improvements and modifications
Merge pull request #1 from jurianeven/mediatag2-2

Mediatag improvements