Added proguard plugin, removed AgeVerificatorFactory.
Renamed interface project to age-verificator to match the class name.
Moved Country into the implementation project, to demo selective proguarding.
Placed Eclipse's binary output to ".target" to prevent it meddling with SBT build.
Added plugins.sbt with Eclipse SBT to all projects.
Added ProGurad SBT plugin to the legal age library project.