migrate dbp, dbo to http

[VladimirAlexiev]

(Related to #44)
dbp, dbo are defined with http in DBpedia, but are used with https in SOA.
You should not modify a property URL when you reused it in your KG.

• This means that a data migration is needed of such props
• And then define the dbo, dbp prefixes appropriately
  • Currently you use dbpedia-owl, dbprop as prefixes, but dbo, dbp are more popular, shorter, and more consistently named