Refactor and organize bootstrap sequence.
Send db init to bootstrap method.
Add test for _init_dirs().
Add test for _init_db().
Add test for _has_symkey().
Add test for _has_privkey().
Add test for _has_keys().
Merge branch 'feature/bootstrap' into develop
Add support for setuptools with fallback.
Fix some comments.
Add dependencies for leap.common and pysqlcipher.
Merge branch 'feature/pysqlcipher-dependency' into develop
Add Twisted as dependency.
Add a LOT of docstrings.
Eliminate the use of super() in main code.

Tests inherited from u1db still use super, but that can be changed in the
future.
Add check for presence of a shared db.
Use BaseConfig for configuring Soledad.
Add events signaling.
Add doc for soledad events.
Remove GPG asymmetric key stuff.

Everything related to asymmetric encryting will be handled by Key Manager.