Full Body Avatar Support

[sebjf]

This ticket is to add full-body avatar support to Ubiq.

Following discussions, @JLPM22 has kindly agree to help implement some of the work undertaken at UPC, specifically,

Combining Motion Matching and Orientation Prediction to Animate Avatars for Consumer-Grade VR Devices   
J. Ponton, H. Yun, C. Andujar, N. Pelechano
ACM SIGGRAPH / Eurographics Symposium on Computer Animation (SCA'2022). September 2022.
Computer Graphics Forum. vol 41(8). pp 107-118

This system enables estimating full body motion from just the head and hands or controllers. The plan is to integrate this into Ubiq's core offering as part of the Avatars system.

To start with, full body tracking will be available but the inbuilt legless avatars will remain the same. In a future update we will aim to replace the inbuilt avatars with full body ones.

The aim is for this system to drive multiple full-body avatar subsystems that users can import on demand from the Samples area of the UPM. We intend to support Rocketbox avatars as a subsystem, and Ready Player Me, to start with. Support for these will also be added after the initial integration of MMVR.

[sebjf]

The fork for building this feature is here: https://github.com/UCL-VR/ubiq-mmvr, though we should keep discussions here as the fork will be deleted once merged.