Use parallelization for multiple project conversion

In the converter tool, the user can provide multiple projects to convert.
At the moment it converts them in a row.
Threads should be used to speed up the process.

Params are used in the [SonarQubeConverter.java](https://github.com/codemetropolis/CodeMetropolis/blob/develop/sources/toolchain/converter/src/main/java/codemetropolis/toolchain/converter/sonarqube/SonarQubeConverter.java) file