default sorting must be set to none in order for views sorting to work

Problem/Motivation

table rowspan settings: default sorting must be set to none in order for views sorting to work correctly.

otherwise it takes precedence and it takes to hours to find out why sorting does not work as set in views.

Steps to reproduce

Proposed resolution

Mention it in readme and on module page.

Remaining tasks

User interface changes

API changes

Data model changes