Tumblr has released a major update to its iOS app for posting to and accessing Tumblr sites. Described as a total rewrite, the new version provides a completely redesigned and simplified interface for managing multiple Tumblr blogs and improvements to Dashboard browsing and posting, including the addition of editing in landscape mode. Users can now also read and reply to messages on Tumblr and find followers via the address book. Tumblr 2.0 is available…