Initial run at hidpi support.
Add cinnamon settings icons to the default icon theme.

This has a few benefits:

- It makes these icon names available to icon sets to override them if desired.
- It delegates the loading of the image files to gtk internally, which correctly
  (and automatically) scales the images for hidpi when defining them by name.
- Launching cinnamon-settings <panel> directly loads significantly more quickly.

And one negative:

- Cinnamon-settings takes slightly longer to load its main menu initially.  I'm
  working on figuring out some way to eliminate or minimize it.
Some cleanup, finish up porting cinnamon settings to hidpi.
menu editor: hidpi support
Restore panel resizing ability, rework their controls a bit.
remove some logging, and some unnecessary stuff in cinnamon-settings
Implement some recent g-s hidpi changes.
Fix panel launcher animation (tween resizing doesn't obey scale), fix alt-tab size
Use svg for stock theme menu icon and mint packaging icon
Fix recent files thumbnails
Improve mouse pointer size configuration.
Fix desktop files again
Fix icon name for new python module