Implement xfwm4 accessibility features

• Configurable key used to grab windows (or disable) (easy_click)
• Hide window frame when maximized (borderless_maximize)
• Tile windows when moving toward screen edge (tile_on_move)
• Use edge resistance instead of snapping (snap_resist)
• Use mouse wheel on titlebar to roll up window (mousewheel_rollup)
• Notify urgency w/decoration blinking (urgent_blink)
  • Keep urgent windows blinking repeatedly (repeat_urgent_blink)
• Double-click actions for titlebar (requires SSDs) (double_click_action)
• Cursor themes