Before this fix, a multi-layer mask move (with mixed layer types:
normal layer and tilemap layers with different grids) caused loss of
drawing areas.

The heart of this solution is to correctly align the 'selection mask'
and 'transform data' according to the layer's grid, and also, forcing
'site' TilemapMode/TilesetMode before each
reproduceAllTransformationsWithInnerCmds() iteration.

The scale transformation could have some things to improve in later
commits. Not fully tested yet.