Deleting a session

Fixed an issue in which sessions couldn´t be deleted. 

UI texts

Fixed an issue when ui texts contains '. This ui ressources can be searched now in Administration - Ui texts without an error.
Also Group Registration - Distribution page updates correctly when ui texts contains ' .

Copying ticket types 
You can copy existing ticket types, everything will be copied with the exception of:

- Amount of saled tickets

- Includes, excludes and required ticket types

Invitation Module

The reasons why somebody rejects a presentation slot or a session chair are now displayed again in the invitation helpdesk.