Release a self-contained bundle/installer

Definition of Done

confirmation for successful installation and launching of Bitmask.pkg, including displaying a working UI (bugs about vpn/mail go on other issues).

Subtasks

• a working bundle (this is already testable with homebrew).
• a signed installer (using Packages)
• a post-install script that installs helpers in its right place
• an statically compiled openvpn #8943 (closed)