Make Titlebar Customization a little more effective - help User to "switch on" title displaying

[xabolcs]

Firefox has browser.tabs.drawInTitlebar for ages. Thunderbird introduces mail.tabs.drawInTitlebar in 17.

Firefox have no title in the following cases:

• "Menu Bar" toolbar is off + drawInTitlebar is enabled
• "Menu Bar" toolbar is off + drawInTitlebar is disabled + no titlebar addon is installed

Thunderbird have no title in the following case:

• drawInTitlebar is enabled

SeaMonkey isn't affected.

Opening up a notification when User opens the Titlebar Customization with some buttons / actions to make the necessary changes would be nice.

Message could be the following:

Titles are not displayed recently. Should Nightly Tester Tools switch back it for You?

Actionable items includes:

• "Do it" - do the magic
• "I've an addon - just switch drawInTitlebar" - Firefox only
• "Not now!" - dismisses the notification
• "Never note this again!" - sets a pref to never open up this notification again

Tracking "Menu Bar"'s visibility is not necessary. In this case the second option above could be skipped too.

[xabolcs]

The second option could be "Install 'Aero Window Title' for me!" which links to bsmedberg's addon.