window-list:  Add an option in cinnamon-settings to disable
alerts in the window-list applet.

Add pulsing effect to window-list item's icon when it wants
attention.

Show off-workspace window-list items in the current workspace's
panel when they want attention.  Clicking on it will switch to
that window's workspace and focus the window.

Add option to turn off window-list alerts

offscreen notifications
Disable windowAttentionHandler - we should allow the user to decide
when to change focus to a window that wants attention.  Also,
if a user has placed a window on another workspace, he/she generally
did that for a reason - we shouldn't force that window back to the
current workspace.

Improvements to the window-list applet make these situations
easier to handle.
window-list applet: Instead of a pulsing icon, simply flash the
standard style change for an attention-grabber.
window-list applet: only flash for a few seconds, then solid attention color
window-list - avoid closing windows that are flagged as needing attention during
close-all and close-other.
Re-enable windowAttentionHandler
window-list: Only listen to urgent signal
window-list - use temporary alert items and left/right alert containers
to handle urgent window alerts
window-list: no right-click menu for alert buttons
Fix some rebase problems... 2 months later!!
[window-list] Check whether window demanding attention has already been noticed.
[window-list] Purge alert-window list of destroyed windows.