Allow to initialize soledad with a blank server
bump version so we can add dependency req in client
Merge remote-tracking branch 'kali/feature/bump-version' into develop
Include testing certificates in package installation.
Use leap.common.crypto and AES-256 CTR for symmetric encryption.
Merge remote-tracking branch 'drebs/feature/2529-use-pycrypto-for-symmetric-encryption' into develop
Change dependency on Twisted to version 12.0.0 instead of 13.0.0
add warning if no shared db found
Merge remote-tracking branch 'kali/feature/blank-server' into develop
Merge remote-tracking branch 'drebs/2528-depend-on-twisted-12.0.0' into develop
Fix various encryption details.

* Use AES256 for encrypting storage_secret.
* Add prepended IV to storage secret's ciphertext.
* _get_storage_secret() returns binary.
* Fix key length when hashing using scrypt.
* Remove password from export/import_recovery_document().
Change symmetric encryption scheme to use AES256.
Add check for encryption method.
Increase storage secret size and use half of it to get the local storage passphrase.
Improve _has_secret() logic and tests.
Improve export/import_recovery_document()

* Fix docstrings.
The IV is now a base64 string
Ensure shared db is created by server.

* Also remove unneeded need_auth() method (because all requests need auth).
* This closes #2491.
Fix tests paths.
Prevent Twisted==12.0.0 from messing with OpenSSL.