Fixes#9219
@JunTaoLuo Dan calls out the implicit versioning "for 2.1 SDK or later;" however, we don't usually version the doc content by SDK release. We might need to say something for this update in the passage that I'm adding to the All topic (*aspnetcore/fundamentals/metapackage.md*) about which SDK version this applies to. I don't know if that's something that you would like to do or what version to call out.
I also remove the version from the samples. We also assume that devs are using the latest SDK with our samples.
* WIP start of XSRF
* MD conversion
* WIP
* Made a lot of progress on filters and javascript impl
* adding sample
* minor updates
* Ajax demo
* Responding to feedback
* Responding to feedback
* Updating JavaScript sample to highlight service injection primarily.
* Updated "session" to "identity" per @blowdart.
Also added a note about use of session elsewhere in the document.
Rick Anderson
Luke Latham