Adding licence header to Muchos files

Using license-maven-plugin we can generate a consistent license header for the project with the following command.

• Temporally convert the project to a maven project. Make sure not to commit the new pom.xml file.
• Via command line, run the following command to generate the license header.

mvn com.mycila:license-maven-plugin:3.0:format -Dlicense.header=contrib/license-header.txt

• Check the output for warnings and manually add the appropriate license to those files.