Add java trace files to refactorings.lib

[LorenzoBettini]

Otherwise opening sources from the dependency won't show the original edelta file (it will show the generated Java code instead).
This requires to compile the .edelta file with xtext-maven-plugin during the build.

[LorenzoBettini]

Better try to leave the trace files in the git repo than to use a JUnit Plug-in test just to generate the trace files