UX in the Roles & Permissions dialog

[maltem-za]

• All team members should be visible immediately, and/or one should be able to search. The menu to add them to the table is sometimes hidden and not obvious/intuitive enough.
• Double-click to change roles doesn't always work. Why is a double-click actually necessary, can we simplify this? Add indication that other options can be selected (eg: down arrow icon).
• Unclear why roles can't be changed at all sometimes (perhaps just missing some indications/feedback).
• Inconsistent menu icon (when compared to the three-dot menu icon used elsewhere) and placement. (This is really a "select visible columns" icon, and is used in one other place that I'm aware of: the tagsets pane in the annotate module.)
• Add link to Roles and Permissions table on website.