Squashed 'Raven.Voron/' changes from facd6bd..d5f9e6e

d5f9e6e write batch - added version to add and delete
bafc665 added test for missing node
1c9055a multitree - concurrency
5fc4ac3 1. fixed an issue when overflow write was performed but split occured 2. added version support for multiadd/delete
6c7ec6a started working on optimistic concurrency
ad3873c fixed page header
50980dc added *.user to gitignore
cbf1cd8 fixed a problem with trees being crated even when transaction is not commited
c010a7a RavenDB-1328. Voron - WriteBatch - error handling

git-subtree-dir: Raven.Voron
git-subtree-split: d5f9e6e1a0b0c1e203dc165fcf0b947821c5647b
Merge commit 'dc044da520adecef190edd2d7860d45bd9583719' into 2.5-voron

Conflicts:
	Raven.Voron/Voron.Tests/Storage/Batches.cs
	Raven.Voron/Voron.Tests/Voron.Tests.csproj
	Raven.Voron/Voron/Impl/TransactionMergingWriter.cs
	Raven.Voron/Voron/Impl/WriteBatch.cs
	Raven.Voron/Voron/StorageEnvironment.cs
	Raven.Voron/Voron/Trees/NodeHeader.cs
	Raven.Voron/Voron/Trees/PageSplitter.cs
	Raven.Voron/Voron/Voron.csproj