Merge #906

906: Cleanup and bugfixes for recently added globalscope functions r=Bromeon a=Bromeon

Addendum to #901.

Changes:
* Documentation for module and special cases of each function
* Fix some wrong implementations (wrapf)
* Fix some doctests not being in triple-backticks, thus not executed
* Limit wrapf/wrapi to non-empty ranges, making them more intuitive
* Add missing polar2cartesian

Co-authored-by: Jan Haller <bromeon@gmail.com>

Author: bors[bot]