Draft: Save long term keyframes

Remaining items (all marked in code as TODO@mateosss)

• Improve dyncast msg
• Pointer output queues in optical flow
• Load map button
• Remove keyframeposes on marg
• Decide next_lmid
• Decide next_kfid
• Decide frame_count
• Decide whether to keep debug matrices of before and after addZeroKeyframeToMargData
• Use binary instead of json? ubjson maybe?
• Generalize last bit of types:
  • load: add to LandmarkDatabaseBase: numLandmarks, getKeyframeIds, getLandmarkIds, assignNewIds
  • load: add to PatchesContainerBase: assignNewIds
  • save: getLongTermKeyframesSubMap to return a LandmarkDatabaseBase::Ptr? careful with refcounting
  • save: add to LandmarkDatabaseBase.getLongTermKeyframesSubMap to return a LandmarkDatabaseBase::Ptr? careful with refcounting
  • save: add to LandmarkDatabaseBase: numObservations, numKeyframePoses, numLandmarks
  • save: add to PatchesContainerBase: numPatches
• Recover pattern case 24, 52, 50
• Build with double
• Fix if (!keyframed && !marginalized && !present) BASALT_ASSERT(false)
• Decide miscelaneous things about behaviour of addMap, assignNewIds, do we want them generic or specific to save-loading?
• is it ok to leave lm.backup fields at zero? or do they have important info
• why linearized==true in PoseStateWithLin
• Try with fixation
• Debug why it bounces off

EDIT: I tidied the UI with subpanels:

subpanels