spices: During installation or updating, do all the dirty work in a tempdir,
so in case something goes wrong, the user doesn't mess up an existing installation
of the applet/desklet/etc...
spices: couple fixes
spices:  Non-system x-lets take precedence over system x-lets.  If a user
downloads a new version of something, hide the system version, as we'll assume
it's not as up-to-date
Cleanup obsolete thumbs in the spices.cache directory when refreshing
Merge pull request #1948 from mtwebster/more-spices

Cinnamon settings:  More spices fixes and tweaks