Separation of compaction implementation to BackgroundCompactor and ManualCompactor
fixing compaction, adding statistics
fixed memtable compaction
fixed the problem with key references in compaction output file metadata
cleanup in compactor
Merge branch 'master' of https://github.com/ayende/temp.raven.storage into testing-compaction

Conflicts:
	Raven.Storage/Impl/StorageState.cs
Merge branch 'master' of https://github.com/ayende/temp.raven.storage