fixed iteration in storage actions implementations so the methods would also take into account pending changes in WriteBatch
Squashed 'Raven.Voron/' changes from f4eccd9..0030c1b

0030c1b added contains method to SnapshotReader that takes into account WriteBatch correctly

git-subtree-dir: Raven.Voron
git-subtree-split: 0030c1bbf23b0b3b8e6d0ff48b05c97621a494ff
Added proper Contains() method to SnapshotReader

Merge commit 'cdd93ee0c530963c43c38775e340aa28d968831c' into 2.5-voron

Conflicts:
	Raven.Voron/Voron/Impl/SnapshotReader.cs
applied Voron changes for Contains method() (take into account WriteBatch pending changes)