Use JavaSE-1.6 EE for all bundles

There are some usages of method java.lang.String.isEmpty() and
java.util.Deque<E> which are available since 1.6.
Juno-based Target Platform
Create initial POMs
Add Eclipse Juno's P2 repository
Add Xtext's P2 repository
Rename TypeValidation to TypeValidationTest

...otherwise Tycho Surefire plugin complains about missing tests and
fails the build.
Generate P2 repository instead of (deprecated) update site
Generate source bundles/features
Configure Tycho's target platform
Use latest Tycho
Add URL to BSD 3-clause license
Minimal config for Travis CI
Don't skip tests on Travis CI