[android] importing jar libraries into android-studio

Avoid redundancy. If you have your jars under /libs in your app build.gradle by default you will have

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    ...
}

that is enough to add all the jars you have under /libs

this is not necessary

//    compile files('libs/activation.jar')
//    compile files('libs/additional.jar')
//    compile files('libs/mail.jar')