Add manual plane detection

[ti250]

Add a feature to tap on a plane to place the drawing surface as a backup to the location by sound/ as an initial setup. (Would also allow faster setup as could use estimated horizontal planes)

[matthewspear]

Simular to the AR Measure App with a selector to pick a position:
https://www.youtube.com/watch?v=z7DYC_zbZCM

Then across devices synchronising a local transform from your local origin to group origin.