Bump externa and add release-notes

Author: dellis1972

.external

@@ -1,2 +1,2 @@
-xamarin/monodroid:fastdevv2@eec40d25b44273888bf4f4d6351974d8cfc5d875
+xamarin/monodroid:fastdevv2@9eb040ae8dd8b703c2466e2c24bf10ef4df9aa65
 mono/mono:2020-02@075c3f06197e3b969f4234d0f56a2e10ee6ee305

Documentation/release-notes/fastdeployment.md

@@ -0,0 +1,15 @@
+# Fast Deployment Updates.
+
+As part of this update the fast deplyment system used for Debugging apps has
+been changed. The shared runtime is now no longer used or required.
+The Platform package has also been make obsolete.
+
+The new system also no longer uses the `external` drive for the fast deployment
+files. All of the files and tooling are now stored in the applications' `internal`
+directory. This has an advantage in that when the application is uninstalled all
+if the files and the tooling will be removed as well.
+
+The new system will not work on any devices older than API 21. This is because it
+relys on features that only work from API 21 onwards. Also API 21 is the lowest
+supported platform for the runtime, so running and debugging on older devices will
+be impossible.