[collections] Add a convenience module.

This module ('collections') re-exports set, bit-set, bit-vector and
byte-vector.
Release note for collections convenience module.
Merge pull request #391 from waywardmonkeys/collections-module

[collections] Add a convenience module.
Merge branch 'user-registry-path' of github.com:cgay/opendylan into user-registry-path
Fix "the the".