ModuleDescriptor.Version is specified as starting with a series of tokens separated by `.` characters, where 'each token is either a non-negative integer or a string'.

However, the `parse` method rejects any version that does not start with a digit:

    jshell> ModuleDescriptor.Version.parse("asdf")
    | Exception java.lang.IllegalArgumentException: asdf: Version string does not start with a number
    | at ModuleDescriptor$Version.<init> (ModuleDescriptor.java:1074)
    | at ModuleDescriptor$Version.parse (ModuleDescriptor.java:1153)
    | at (#2:1)

The documentation should reflect this fact (or the implementation relaxed).