Apps in flutter/samples should use the new application template

[mit-mit]

https://github.com/flutter/flutter/pull/22565 landed a new default flutter template. This allows us to not have to check-in android and ios directories when they have just default content. We should update the app samples in https://github.com/flutter/samples to use it.

[redbrogdon]

@domesticmouse You just did a bunch of work recreating project structure for the older samples -- are we good on this?

There should only have been a few sample apps before the Flutter Live release of the SDK.

[domesticmouse]

I believe so. I’ll rebase all the projects again when the next stable release happens.

[redbrogdon]

(furiously scanning through GitHub history)

There were only six samples in the repo at the end of 2018. Of those, two no longer exist and three have updated metadata. Only place_tracker's .metadata file is older than the December '18 stable release. That should reflect the last time it was updated.

So it looks like we still have a tiny yak to shave. We can get to it the next time we have a maintenance jam. We also need to update that app to use a more standard state management approach anyway.