Repos.create() shouldn't require usage of raw JSON

[cvrebert]

Repos.create() currently accepts a raw JsonObject as its argument. This is annoying to work with and not very typesafe. It would be better if it accepted a structured, well-typed object instead.

[dmarkov]

@rultor rultor closed it by mistake, @cvrebert please take a look

[cvrebert]

Again, not a mistake.