Use scrypt to derive key for local encryption.
Merge remote-tracking branch 'drebs/feature/2716-use-raw-sqlcipher-key-with-scrypt-as-kdf-2' into develop
Move symmetric encryption/decryption code from leap.common to leap.soledad.
Remove strict dependency on leap.common.

* Encapsulate leap_assert and leap_assert_type so Soledad works without them.
* Remove dependency on leap.common.files.mkdir_p().
* Encapsulate signaling.
* Add changes file.
Update dependencies.
Merge remote-tracking branch 'drebs/feature/2602-remove-strict-dependency-on-leap.common-2' into develop
Remove unneeded imports from Soledad tests.
initscript: remove unnecessary backslashes in variable definitions
initscript: replace environment variables with more standard upper-cased names
initscript: make a TWISTD_PATH environment variable to replace hard-coded /usr/local/bin/twistd
initscript: pull environment variables together into one block
initscript: move HOME variable up to environment variable block, remove unnecessary double-quotes
initscript: add LSB (Linux Standards Base) 3.1 compliant header
add changes file detailing initscript enhancements
Add encrypted sync test case.
Merge remote-tracking branch 'micah/feature/improve_initscript' into develop
Add changes file.
Merge remote-tracking branch 'drebs/feature/2710-add-encrypted-couch-sync-test' into develop
Do not list the backends as __all__