* android templates should add density and screenLayout to config changes

* update the rest of the manifests

This reverts commit 36e3b103 to make the build green.

This reverts commit 25b1d43a.

This reverts commit 05d6b08f.

This consolidates all of the non-template .gitignore rules into the top level .gitignore, to ignore common things more broadly, with less maintenance needed for the .gitignore files. Does not touch the templates, so that they still produce needed .gitignores as part of flutter create.