fixed #1263
fixed #1260
fixed #1293

Why, oh God, why?! #thanksjamesgosling

This also ensures that the IV is generated with proper randomness.

If there are no UNDECIDED keys, but none of the contact's keys are
trusted, redirect the user to the TrustKeysActivity

Can now long-press a key to permanently purge it.

* CryptoNextBeta: (60 commits)
  Lock TrustKeys if no trusted keys are available
  Optimize imports
  Use MD style for key trust toggle switch
  Fix set/remove OnUpdateBlocklistListener
  Fix axolotl database migration
  Remove device list from EditAccount
  Add clear devices to overflow menu in EditAccount
  Ask for key trust when sending messages
  Encrypt files for HTTP upload in encrypted chats
  Refactor trust key ui and show in account details
  Send correct body for HTTP files
  Handle file transmission properly in axolotl
  Remove unneccessary code
  Fix trust status for outgoing messages
  Don't merge messages with different trust statuses
  Fix copying of axolotl keys to clipboard
  Add refresh icon to v21 theme
  Disable Axolotl option if not usable
  Show trust status of messages' originating session
  Add key trust toggle to ContactDetailsActivity
  ...

show contact details in conference details ...

Can't call getWritableDatabase in recreateAxolotlDb()

Change CAB to accent color in v21

If the contact (or the own account) has keys that have UNDECIDED trust,
we now drop the user into the new TrustKeysActivity, where they have to
decide for each new key whether it should be TRUSTED or UNTRUSTED.

Refactored the trust key row UI element so it can be used in multiple
places. It now also uses a slider to toggle the trust state, and the
redundant trust state description was removed.

EditAccountActivity now shows the keys of other devices associated with
that account.

When using HTTP upload to send files, take care to transmit only the URL
rather than the entire body, which contains metadata.