Lots o' Goodies & Translations

Lots o' goodies:

• The last-used browser is remembered for next time
• New "Reset Preferences" menu item and dialog
• Ctrl+O to open the current page in another browser
• Refined (ever-so-subtly less flat) HeaderBar design
• Ephemeral is now translatable!

Translations:

• ¡Hola! Spanish translations thanks to @fitojb and @capitantrueno
• salut! French translations thanks to @NathanBnm
• Olá! Brazilian Portuguese translations thanks to @sanchezlucas
• Hallo! Dutch translations thanks to @Vistaus