doc/windowbehavior: improve help page for window behavior kcm

• add missing entries for focus delay and multiscreen behavior
• add missing entries for window placement modes maximized and under mouse
• add missing entries for mouse actions
• remove entry for removed "display window geometry when regeometrizing" option
• reword explanation for window raising
• extend explanations for window placement
• hint at screen edges kcm in movement section
• hint at window rules in advanced section
• add more keywords
• some small wording, typographical and formatting changes