Offline support for mobile

[tobiasKaminsky]

Currently when mobile apps have no data connection nothing can be done. Nevertheless we can allow some things for user

• [ ] cache up until e.g. 200mb of metadata of files/folders, so that user can browse them, with latest state
  • regularly update
  • update newest first
• [ ] allow to upload files
  • will then be directly queued
  • not shown as error
• [ ] allow to create folders
• [ ] make sure that other tasks are not shown (e.g. create rich workspace info, as this requires online text editor)
• [ ] handle online/offline better
  • show it better to user
  • restart uploads/create files upon reconnect