2.0.0: Replace request package with cross-fetch

rokka.js uses now cross-fetch instead of "request" for making the actual http calls. It's much smaller as the main reason.

The object returned as response in the Promises therefore also changed. We tried to make it as backwards compatible as possible with providing the relevant properties as before, but we can't guarantee 100% BC, therefore release a major new version. If we missed something, tell us, and we can add it.

Additionally rokka.sourceimages.get now supports query parameters for supporting deleted. Also added that support to rokka.sourceimages.list

Also added rokka.memberships.get(organization,userId)