Sound applet: do a full rescan when a sound card is added or removed

When adding a sound card, associated sinks weren't appearing in the "Output device..." menu because nothing was connected to the card-added signal.

This commit plugs card-added and card-removed to the same function as state-changed.
A few fixes for the user applet
Allow passing of media keys to cinnamon-settings-daemon, and setup a
few initial media keys.  More can be added as desired.
Simplify dbus method call
Add a fix for the menu applet
Add some more keybindings
Merge pull request #2270 from mtwebster/gnome-dbus

Allow use of media keys during Cinnamon modal states (menus open, etc..)
Merge pull request #2264 from deubeuliou/patch-1

Sound applet: do a full rescan when a sound card is added or removed
Some changes for cjs
Automatically enable the panel launchers applet when it isn't and "add to panel" is selected in the menu
Merge pull request #2275 from mtwebster/cjs

Changes necessary to use cjs instead of gjs
Ensure modal windows made by cinnamon get focus correctly when using a full
screen program.  For example, watching a video fullscreen, then alt-tabbing,
without this patch, most times, the alt-tab popup won't appear, even though it
will function.  With this patch, alt-tab properly shows above everything
Clean up cs_settings.py, remove a lot of duplication
Align UI in cs_effects.py. Change some packing options in SettingsWidget.py to make that possible
Merge pull request #2286 from mathrick/hig-cleanup

HIG cleanup
Merge pull request #2284 from mtwebster/disable-unredirect-on-modal

Ensure modal windows made by cinnamon get focus correctly when using a full screen program
Replaced GNOME "User Accounts" with new Cinnamon "Users and Groups"
Couple of fixes in user and user-groups modules
Merge remote-tracking branch 'upstream/master' into panel-rework