Permissions Page improvements

[vrichter]

This idea has been developed and deployed to Canvas

Freeze the column headings when you scroll down the list of permissions so it is easier to know which permission you are adjusting.  Presently, one has to count columns and then remember which one to change, since the role names scroll off the page as one moves to the bottom of the ever-expanding list of permissions.

Comments from Instructure

For more information, please read through the https://community.canvaslms.com/docs/DOC-14928 .