Update docs and release notes for 0.4.0

Change-Id: Iad6cfe5dee63adb9e60a0ea9811217b3175eb99c
Merge branch 'v3-group-user-list' into dt-test
Merge branch 'release-0.4.0' into dt-test
Merge branch 'new-session' into dt-test
Merge branch 'identity-ec2-tests' into dt-test