rotomap.relate: best_theory incl. known mapping
rotomap.relate: best_theory incl. known mapping

When generating theories with best_theory(), also include the 'default
theory', which takes into account the moles that already have the same
uuid. This leads to better results with 'mel-debug bench-relate'.

Test Plan:
.. 'bench-relate' before and after, see big improvement ..
.. 'mel rotomap-autorelate' a rotomap successfully ..
.. 'mel rotomap-edit' and 'follow paste' successfully ..

aevri/mel,aevri/mel