Change default generated app to build a generic target

[grepsedawk]

This allows for easier devops/DX by being able to have a reliable bin/app generated on build
Which greatly cleans up universal Dockerfiles

Resolves #735

[jwoertink]

I think there's a few other places this has to be changed. Like

lucky_cli/src/web_app_skeleton/Procfile.ecr

Line 1 in 0b5b8fb

web: bin/<%= project_name %>

for example

Also, I forget, but maybe the Heroku buildpack may also need to be updated? I'll try to dig around the ecosystem a bit and see where all this gets used. Thanks for getting this started!

[grepsedawk]

I'll grep for project_name and see if I find other places.

[grepsedawk]

Ooh nice, one .ecr taken away, certainly a win in my eyes
@jwoertink didn't find any other refs that need to change

[grepsedawk]

Oop, forgot to mark this as ready for review

[jwoertink]

👍