Exclude $vector and $vectorize from the default Projection

[tatu-at-datastax]

(note: depends on #1001)

Since fields $vector (and soon to be added $vectorize) are rarely needed by most users and (equally importantly) are generally large and heavy-weight to process, let's make them "exclude-by-default" -- reverse of _id "included-by-default".

This means that without Projection definition, they would not be included in output but instead need to be explicitly included (except for #1001 which will add a short-cut for forced inclusion).