add unit tests
add dummy class AbstractKeyAction to satisfy compiler, needs to be refactored
organize imports
uncommented code to satisfy compiler
fix documentation and code formatting
add class PluginIdentifier
equals and hashCode
refactor getLanguageName() -> getName()
refactor class Language
refactor class Language:
- comment out/remove code to satisfy compiler after refactoring
- remove test class LanguageTestImplementation
add Groovy support for writing unit tests with Groovy