Blender Git Loki

Fix new UI align code behavior with very small buttons.

In case two neighbor buttons are very small, their total width (or height) can remain below
max authorized delta, and hence wrong side could be detected as 'common side' for the pair.

This is now fixed by checking both opposite sides at once.

Also, we expect buttons to have some width and height to be considered alignable now!

Took me two days to sort that out, grrrr!