Remove now obsolete import to ville-theme.scss from vexer-archetype
Update documentation of vexer-model classes

Updated the JavaDoc-strings of vexer-model classes, also added missing
Serializable-declarations
Added JavaDoc to VilleExerStubUI.getLocalesToTest()
Clean-up of archetype-poms
Added isManuallyGraded-method to vexer-model.ExerciseTypeDescriptor

The method tells which exercise-types require manual grading by
a teacher and which can be automatically assessed
Update vexer-template to implement new isManuallyGraded-method
Added a template .gitignore file to vexer-archetype

Added .gitignore file that will be included to projects
generated from vexer-archetype
Bumped to version 0.0.4-SNAPSHOT