Several fixes before pull request

Move Crossplane installation doc/charts/archives to another place (oam-dev, addon-local or any other place), to ensure this repo is kpt + application model only
The README should be kpt + application model steps, not install Crossplane
Add a graph to clarify the relationship between kpt and application model (i.e. manipulator and data)
(Do in parallel) Move Crossplane installation doc/charts/archives to here
(Final) https://github.com/GoogleContainerTools/kpt/tree/master/site/content/en/guides/ecosystem

wonderflow / crossplane-oam