Finish alignment layers

@mortenvp @jpihl I found an elegant solution for testing all region methods in TestRegionEqualAlignment. I used inheritance instead of the 7 template parameters ;)
I will use the same approach for the other 2 unit tests. It should be straightforward with the region_dummy.
I also found a bug in region_divide_alignment where the unaligned head was calculated incorrectly if the alignment was correct. That certainly made things slower.