Provide a way to serialize version into comparable strings

org.xwiki.extension.version.Version are comparable and can easily be sorted in java.
This is not the case when versions are stored in third parties such as databases or solr, where no specific sorting is available.
Therefore, it is interesting to allow versions to be serialized to a format which can be compared alphanumerically while preserving the versions sorting semantics.
To do so, I propose to serialize versions in the following way:

• 1.1 would become 000001-000001
• 1.1.1 would become 000001-000001-000001
• 1.10 would become 000001-000010
• 1.4-alpha3 would become 000001-000004-alpha-000003