Kitodo.Production 2.3.1

This is a bugfix release

• rename temporary image file extension to "jpg"
• Delete old temporary images
• Prevent Null Pointer Exception if meta data value is null
• Fix editing of properties in current task
• Initialize current step access condition for existing properties
• Better explain parameter useMetadatenvalidierung
• Better explain folder creation parameters
• Support defaultDisplay on metadata groups
• Change if inside if to if-else if
• No longer disclose credentials on the start screen
• Remove default users, rename admin and LDAP group
• Use configured DIRECTORY_SUFFIX anywhere

Instructions for installing:
https://github.com/kitodo/kitodo-production/wiki/Installation-instructions-for-Kitodo.Production-2.3.1