Release 0.9.19

Parallel Virtual Cluster version 0.9.19

• [CLI] Corrects some flawed conditionals
• [API] Disables SQLAlchemy modification tracking functionality (not used by us)
• [Daemons] Implements new zkhandler module for improved reliability and reusability
• [Daemons] Refactors some code to use new zkhandler module
• [API, CLI] Adds support for "none" migration selector (uses cluster default instead)
• [Daemons] Moves some configuration keys to new /config tree
• [Node Daemon] Increases initial lock timeout for VM migrations to avoid out-of-sync potential
• [Provisioner] Support storing and using textual cluster network labels ("upstream", "storage", "cluster") in templates
• [API] Avoid duplicating existing node states