all key types changed to string
fixed failing tests
fixed missing key conversion
added null guard to Command<>
updated changelog
updated changelog again :)
Merge branch 'master' into feature/string-aggregateroot-keys

Conflicts:
	CHANGELOG.md
	d60.Cirqus.AzureServiceBus/Relay/AzureServiceBusRelayEventStoreProxy.cs
	d60.Cirqus.MongoDb/Events/MongoDbEventStore.cs
	d60.Cirqus.PostgreSql/PostgreSqlEventStore.cs
	d60.Cirqus.SQLite/SQLiteEventStore.cs
	d60.Cirqus.Tests/Contracts/EventStore/EventStoreTest.cs
	d60.Cirqus.Tests/Diagnostics/TestProfiler.cs
	d60.Cirqus.Tests/Events/Replicator/ErrorHandling.cs
	d60.Cirqus.Tests/Snapshotting/TestSnapshottingWithFairlyLongHistory.cs
	d60.Cirqus/Diagnostics/DiagnosticsConfigurationExtensions.cs
	d60.Cirqus/Events/IEventStore.cs
	d60.Cirqus/Extensions/EventExtensions.cs
	d60.Cirqus/MsSql/Events/MsSqlEventStore.cs
	d60.Cirqus/Ntfs/Events/DataStore.cs
	d60.Cirqus/Ntfs/Events/NtfsEventStore.cs
	d60.Cirqus/Testing/Internals/InMemoryEventStore.cs
fixed errors introduced after merge w master