Get rid of project.properties files

The properties should be read from Gradle files such as `gradle.properties`, `settings.gradle`, or defaults in the root `build.gradle` file.

P.S. This means that default compile SDK version should be read from root `build.gradle` (copied from `bin/templates/project/build.gradle`) instead of `project.properties` file.

Start by tracing how properties are currently read from project.properties, then compare gradle.properties, settings.gradle, and the root build.gradle. Check bin/templates/project/build.gradle for the copied defaults, especially the compile SDK version. Done means project properties, including the default compile SDK, are sourced from the Gradle files without project.properties files.

Written by the indexing model from the issue text.