Prevent ArrayIndexOutOfBoundsException during Module quick-fix
Ensure that validation runs when metadata.json is missing

The xtext build participant was configured to run only when file
extension "json" was found in the project. This commit changes that
so that it runs on all projects and then reacts to natures in the
project.
Add 'build' and 'module_build' to deprecated metadata fields
[GEP-155] Remove all references to deprecated v2 API
[GEP-267] Use UTF-8/LF as the default on all platforms
[maven-release-plugin] prepare release geppetto-4.2.0
[maven-release-plugin] prepare for next development iteration