0.8.17.40507 - Improvements for full body and avatar anchors

- Added "Use Symmetry" for avatar calibration in the full body calibrator, which will move the feet and knee offsets symmetrically
- Added skeleton visualization to the full body calibrator, for both reference and calibrated avatar
- Added "UnparentEverythingOnDestroy" option to AvatarAnchor. This will unparent any objects in the user root when the anchor is destroyed. This prevents any items spawned or created while under avatar anchor from being destroyed along with it
- Added "Generate Debug Visuals" to Rig and BipedRig in the inspector, which allows generating temporary skeleton visuals for debugging purposes


- MultiUserAvatarAnchor will now filter out second pointer if one is already pointing at it, preventing the highlight point from jumping around
- Automatic avatar hips/feet calibration will now replace old calibration in cases where the rotation is close enough, but the offset is too large
- Improved automatic calibration of hips for avatars where the hip bone is too far up the spine
- Added cross bar to avatar calibration references to better visualize their orientation
- Added labels to avatar calibration references (tracker labels will be hidden when calibrating avatar)


- Fixed random bone drift for IK avatars, causing some parts of the body to randomly become elongated or shortened (reported by @RaccoonRezillo and @Reks )
- Fixed sent invite messages showing incorrect timestamp in the history (reported by @AlienInArea51 (MR-Alex) )
- Fixed spelling error on RandomObjectSpawner (reported by @NotMeCoffee )
- Fixed exception in UserDistanceValueDriver when user root is missing (e.g. on headless or when respawning) (discovered in log from @tehturk )
- Fixed MultiUserAvatarAnchor breaking when the anchors root has children that are not anchors
- Fixed OverlayFresnel writing into ZBuffer when opaque, preventing it from functioning properly
- Fixed GetChildrenWithTag() not searching children correctly
- Fixed incorrect positioning by hips for full body avatars, which should fix pose problems with certain avatars when entering avatar anchor
- Fixed full body calibrator not resetting reference visual correctly after avatar calibration is finished