sound applet: linuxmint/Cinnamon#2170 instead of hardcoding the default theme, Gtk search pathes are used instead to use the icons in the current theme, for icons player-*
sound applet: linuxmint/Cinnamon#2170 instead of using theme defined icons, symbolics media-playback-* are used
sound applet: fixed variant number two, TextImageMenuItem had an argument too much
xlets: Add better error handling and reporting.

    - At the end of Cinnamon startup, show a notification if any applet,
      desklet or extension has failed to load.
    - In spices, show an 'error' status for items that *should* be running,
      but are not actually currently running in Cinnamon.  Prevent adding more
      instances or configuring these items.  Hopefully this should prevent
      issues such as #3568.
    - In spices, detect when a newly-enabled xlet has failed to load, disable it,
      and notify the user, with an option to view log files (this will need fleshed
      out for other distros.)
Enable looking glass logfile by default.
spices load error dialog: Fix default response button, don't close dialog
when log button is pressed.
Test script: Don't remove spices (that removes cinnamon-bluetooth and 3rd party spices using @cinnamon.org in their UUID)
xlets: fixed desklet loading (regression from c3cc4c6)
touchpad: Allow user to define what button  2- and 3-finger click
emulates
extensions: fix issue in error-handling (ref c3cc4c6)
Merge pull request #3593 from pixunil/sound-applet-theme-issue

Fixed #2170: sound applet player status icons
Cinnamon Settings: mintdrivers link label "Device Drivers" -> "Driver Manager" (consistent with mintdriver's .desktop file)
Merge branch 'master' of github.com:linuxmint/Cinnamon