Wrap-up changes for updated subfolders

[artonge]

Add changes to support sharing and sub folders brought by the v2 encryption format.

• Add special handling for unsharing files fromE2EE folders, which conflicted with the deletion process
• Support wrapping up changes for subfolders
• Add counter logic to prevent overriding more recent metadata, and prevents rollback attacks
• Add signature logic to protect against metadata update from unauthorized parties
• We need to support v1 and v2 encryption version, so we duplicated some code
• List of changes per files:
  • MetaDataController
    • Add support for signature
    • Improve locking logic for filedrop updates
  • MetaDataStorage
    • Add support for signature and counter
    • Keep track of touched folders
  • LockingController
    • Add support for counter
    • Support aborting changes during unlock
    • Support finalizing changes in touch subfolders
  • LockManager
    • Check counter when locking file
    • Add possibility to assert locked by token in isLocked
  • V1/MetaDataController
    • Improve locking logic for filedrop updates
  • MetadataStorageV1 // No changes
  • V1/LockingController // No changes
  • LockStorageV1
    • Add possibility to assert locked by token in isLocked
  • RollbackServiceV1 // No changes
  • E2EEPublicShareTemplateProvider
    • Add encryption version and users public keys in initial state
  • Front files: adapt to new API requirements
• ClientHasCapabilityMiddleware --> Return an error to old clients when they access a v2.0 encrypted folder.

Fix:

• Allow unlocking a folder with rollback of metadata #438
• Implement headers X-NC-E2EE-SIGNATURE and X-NC-E2EE-COUNTER #437
• Unlock folder without token leads to 404 #479

[artonge]

/rebase

[susnux]

Frontend look good, just some minor comments

[artonge]

/backport to stable28