Revert "Binary support in BSON (dev bundle wise) and in Mongo"

This reverts commit c10c7f7c9131ff7c45342cf11c8f51085cbbcf71.

Only revert the non-test portions, leaving failing tests. Will implement
binary-in-Mongo in a different way on this branch before merging back to
ddp-pre1. (Assuming that works, will also delete the 0.2.15 dev bundles from s3
and production.)
Replace Mongo binary types with Meteor binary types on the way in and out of
Mongo.

(Should consider doing the same with ObjectId.)

(Also, still need to delete 0.2.15.)