Removes unintentional empty projects

[tresat]

See: https://docs.gradle.org/current/userguide/best_practices_structuring_builds.html#avoid_empty_projects.

There were :game-app, :http-clients and :lib projects created that weren't necessary.

This also avoids the need to type out :game-app:game-core, and instead allows the use of just :game-core.

Most important, it stops Gradle from assuming these 3 dirs contain Gradle projects, which they don't, improving performance and comprehensibility.

[tresat]

Some common objections to this are:

• Now I can no longer see project grouping via the name. If this is important, we can rename + relocate to include some prefixes, for example: /game-app/game-core could move to /game-app/app-game-core and /lib/java-extras could move to /lib/lib-java-extras.
• Now there might be name collisions, between a project in /game-app and one in /lib. Prefixes avoid this, but it's not yet a problem.

Another common pattern is to add the prefixes, then relocate ALL projects into a /subprojects root dir. This presents a nice IDE experience, when navigating source code, and keeps the top-level dirs from multiplying.

[DanVanAtta]

@tresat this update seems interesting, if you want to clean it up, I don't have any particular objections.

[tresat]

This one I expected to be more "controversial". I think it's a good idea, but the other 2 PRs I've got open should go first, then I can clean this one on top of them.