Initial packaged release

Functionally complete initial package:

• Includes support for custom scripts to handle attach-, detach-, and detach-abort events, which can be configured in /etc/surface-dtx/surface-dtx.conf.

• Includes systemd unit file (surface-dtx.service) for ease of use.

• Notifies the user via dbus notifications when the clipboard can be detached, or the re-attachment procedure has been completed.