Code to handle import and export of settings
Only import wanted options
Only export wanted options
Make export.js a module
Add new thumbnail pref to export
Fix export.jsm so it can be called from anywhere
Remove calls to alert from export.jsm
Localise import/export dialogs
Copy locale files to other locales
Add buttons to preferences pane for export and import
Merge branch 'export' into unreleased
Fix packaging
Fix error when there is no background image