* changed to using pictureHashes as ids for pictures
* ry_pictures contains extra columns for location info and make model + mapping from internal id to hash
* chats and submissions have internally a pictureId for efficient organization in DB, externally pictureHash
* PictureLink pattern re-used to add hash-id mapping if picture was uploaded
! pictures are only saved if the picture was uploaded successfully (TODO: save to db), to allow for renaming in case of duplicates
* rewrote ImageRepository to cache byte[] scale images lazily
! no detection of duplicate hashes
+ support for preview uploads
+ logging exceptions in DataAdapter!