Javadoc sanity check #35
Description
Some of the Javadoc comments are out of date and contain false information. F.ex. see fi.helsinki.cs.tmc.core.commands.Command#L51-56, fi.helsinki.cs.tmc.core.commands.DownloadExercises#L119-124 and fi.helsinki.cs.tmc.core.exceptions.TmcCodeException. Furthermore, multiple classes have undocumented public methods. These need to be updated and documented.
It would also be nice if the comments used Javadoc tags, especially for links to other classes within the project.