Change the default location of close buttons to the left

[Croydon]

For the majority of users of VTR the default location of the sidebar is on the left (this depends on the locale of Firefox). Displaying the close button by default on the left side of tabs, has the advantage when an users moves it's mouse from the website area to the sidebar, that they are not on the close buttons first and have to be careful to accidentally hit them instead of switching to another tab.

Of course, all users continue to be able to change this setting.