Improvements
* resolve 4636 environment variable expansion for pkgs_dirs (4637)
* link, symlink, islink, and readlink for Windows (4652, 4661)
* add extra information to CondaHTTPError (4638, 4672)
Bug Fixes
* maximize requested builds after feature determination (4647)
* fix 4649 incorrect assert statement concerning package cache directory (4651)
* multi-user mode bug fixes (4663)
Non-User-Facing Changes
* path_actions unit tests (4654)
* remove dead code (4369, 4655, 4660)
* separate repodata logic from index into a new core/repodata.py module (4669)