Reworked Ticket creation

- Error handling
- Error message design with Joomla alert class
- Dont use Joomla Editor, better use textarea in Form
- unnecessary to include validateEditor with Joomla function
- Form Validation: Subject min 5 Chars
- Form Validation: Message min 20 Chars
- Form Validation: Attachments max 4MB

ToDo: Form Validation in Javascript is a bad solution, should be checked
serverside.