VersionInfo string representation

[smarie]

It seems that the string representation is not available from VersionInfo. It should be quite straightforward to do with a custom string representation method:

def __str__(self) -> str:
    return (str(version.major) or '') \
           + (('.' + str(version.minor)) if version.minor is not None else '') \
           + (('.' + str(version.patch)) if version.patch is not None else '') \
           + (('-' + str(version.prerelease)) if version.prerelease is not None else '') \
           + (('+' + str(version.build)) if version.build is not None else '')

Note that we can keep __repr__ untouched so that it provides unambiguous representation.

[scls19fr]

__hash__ should also be implemented #73 (probably with a similar method)