unity upgrade script doesn't reset metacity settings

[Marco Trevisan (Treviño)]

When upgrading ubuntu 10.04 to 12.04 unity correctly imported some old desktop settings, but didn't reset these *metacity* parameters, causing some visual inconsistencies with wanted design:

 - The theme was not reset to ambiance/radiance
 - The font (and so the font used by the unity panel) was not set to Ubuntu
 - The button layout was not updated (and so they were on the top-right corner of the windows)

The unity script should take care of resetting the relevant gconf keys:
 /apps/metacity/general/button_layout (should be "close,minimize,maximize:")
 /apps/metacity/general/theme (should be "Ambiance" or "Radiance")
 /apps/metacity/general/titlebar_font (should be "Ubuntu Bold 11")