Added export and import of repositories.

The goal of this work is to provide the ability to export the known list of hg repositories from one workspace so that they can be imported in another workspace without having to manually recreate each repository in the second workspace.

I took the opportunity to perform some extensive refactoring, over SonarQube reports of code smells and other dubious code. This has the drawback that the actual code of this feature is lost among all those changes. I'll try to find a better way to incorporate such code cleaning actions.