Easter Release

!Attention! Please backup all data before updating !Attention! Due to a bug in the auto updater, an update from a commit version before january 29th 2019 will lead to loss of all data

• Update search function for Unicode characters
• Upload of jpeg, png and webp file
• Extraction of png covers from pdf files during upload
• Updated epub reader lib
• Fix for sqlalchemy v1.3.x
• Removed Douban from metadata loading
• Fixes for OPDS feed
• Improved errorhandling
• Changed behavior of filename renaming on Google Drive to match renaming on normal filestorage