[ArisMorgens]

This PR adds the basic functionalities of the Lighthouse Positioning tab to the cflib2-based cfclient. The geometry-estimation-related features are not part of this PR, as we first need to decide on where the helper files should be hosted.

This PR is based on this cflib2 PR.

Differences compared to master:

• A bad config file shows a pop up error instead of a traceback in the console.
• You get a warning for rejected geometry and when saving to permanent memory fails. Master ignored both.
• Only slots that were written are persisted. The effect on the drone is the same.
• Import and Export are disabled while one is running.
• Memory accesses take turns, since 2 users can't access it at the same time.
• In the 3D view, the rotation comes from a new small function _rpy_to_rot. On master, this was done with cflib's Pose.from_cf_rpy().

The added files are formatted according to pre-commit.