apps-menu: don't store the hot corner at creation

HotCorners become invalid when the xrandr configuration changes,
so instead of storing it fetch it directly from layoutManager when
needed.

https://bugzilla.gnome.org/show_bug.cgi?id=702038
alternative-status-menu: unpack the result of CanHibernate

The DBus call yields a GVariant, which we need to unpack to
obtain the JS value to compare.

https://bugzilla.gnome.org/show_bug.cgi?id=702300
user-theme: look for gnome-shell themes in ~/.local/share too

Just like we look in XDG_DATA_DIRS, we should honor XDG_DATA_HOME
as well.
For compatibility reasons, we look in ~/.themes first, then ~/.local/share,
then /usr/share.
systemMonitor: don't propagate clicks up

Otherwise you get gnome-system-monitor and a message tray menu.
xrandr-indicator: stop processing RandR events when disabled

It's hard to tell people to disconnect their signals, when we
are the first to forget it...
xrandr-indicator: fix syntax error

It shows the level of testing or usefulness this extension has...
Bump version to 3.8.4