Added constant holding the starting version string we give to any new prerelease version.
Implemented a working Version.GetNext for the case when there is no "current" version given, i.e. we always start from the beginning of the series.
Extended Version.GetNext to support the case where the specified version and the current one does not match, indicating we need to restart a new CPV sequence.
Finalized a first working, but still a little messy implementation, of Version.GetNext(string).