Prepare package.json for vibe.d support and for publishing.
Make the library compile with and without vibe.d.
Avoid warnings during the build.
Add port-less overload of `connectMongoDB`.
Add DDOX options so that "dub --build=ddox" produces output also for undocumented members.
Move modules that are not for public use into an "internal" package.
Make internal functions in cassandra.cql private.