AndroidTopProject, project1, project2 all come from a SO post, If you go into AndroidTop there is a README w/ the explintaion and a link to the question NDK Project shows you how to use Gradle and the NDK (until google releases NDK support in Gradle)
hiAndroid/AndroidComplexBuild
Based on StackOverflow Question http://stackoverflow.com/questions/17536652/gradle-and-multi-project-structure
GroovyNOASSERTION