Squashed 'Raven.Voron/' changes from 7addb35..2761b28

2761b28 fixing issue with recursive page splitting
5927199 another page splitter issue that occurred after recent fixes
183243c fixed issue with page splitter not calculating separatorKey correctly
a4a9fe0 cleanup
e569565 exposing very strange issue
ac44cbd cleanup
629e5b8 fixed issue with removing MultiTreeRef node from page

git-subtree-dir: Raven.Voron
git-subtree-split: 2761b289fd9916ccba7cc92bc82c90fff2894cff
Merge commit 'eaa3e67a5956489cbdc20e81262a9009cd1ad27c' into 2.5-voron

Conflicts:
	Raven.Voron/Voron.Tests/Voron.Tests.csproj
	Raven.Voron/Voron/Impl/SizeOf.cs
	Raven.Voron/Voron/Trees/PageSplitter.cs