docs/releases/tsuru-admin: fix copy and paste issue

It's tsuru-admin, not tsr :)
docs/releases/tsuru-admin: fix links in the notes for 0.3.0
docs/managing/add-platform: fix link
docs/releases/tsuru-admin: fix links in the notes for 0.4.0
docs/releases/tsuru-admin: finish notes for the 0.5.0 release
docs/reference/tsuru-admin: sort commands