fix insert new entry in preview

• using the current template and inserting at the right position
• update model
• cleanup
refactor saving to make more secure and precise

• replace unspecific fromArray by setting each value safely
• cleanup
• add new widget css class “reset_padding” to allow list widget to take the full space of the accordion panel
improve validating and saving of data

• replace fromArray by specifically setting and handling each value
• throwing validation exception when is_published is set and no text content given