Versioning Algorithm

This is the versioning algorithm part for versioning the GDM.

note: this algorithm is probably incomplete, contains errors or doesn't reflect the current implementation state, which is available at dswarm-graph-neo4j; so please, take this information with care ;)

1. fetch latest version from data model node (+ increase this value + update resource node (maybe at the end))
2. compare existing resource DB statements with new resource DB statements, i.e. write/follow statements ordered by index property (it might be good to also have the relationship in the permanent DB that is related to this index available)
   1. if a statement was added or deleted or the printed version doesn't equal, rewrite all following statement afterwards and deprecated the existing ones (i.e. update their valid to value) for added + modified statements utilise the current version for valid from

TODO: enhance this algo description ;)