* added readwritelock that properly supports async/await
* RavenDB-865 test passing
Merge branch 'New3' of github.com:ayende/ravendb into New3
make AsyncReaderWriterLock compile with Silverlight
proper fix for DateTimeOffsetIssues unit test
minor fixes related to RavenDB_1007 (also passes with Voron)
AttachmentContentType tests are passing (attachment metadata now overwrites matching http headers)
Merge branch 'New3' of github.com:ayende/ravendb into New3

Conflicts:
	Raven.Abstractions/Json/Linq/Extensions.cs
minor
Merge branch 'New3' of github.com:ayende/ravendb into New3

Conflicts:
	Raven.Client.Lightweight/Connection/Implementation/HttpJsonRequest.cs
	Raven.Database/Server/Controllers/StaticController.cs
	Raven.Tests/MailingList/AttachmentContentType.cs