Fix install-dir to not use Impl entity suffix

- Adds EntityType.getSimpleName
- Use entity.getEntityType().getSimpleName(), rather than doing
  entity.getClass().getSimpleName()
EntityType.getSimpleType: incorporate review comments

- Also converts EntityTypeTest from groovy to java
Merge pull request #540 from aledsage/fix/InstallDir-DoNotUseImplNames

Fix install-dir to not use Impl entity suffix