Adds a setting to toggle displaying the battery percentage and also limits it to only display the internal batteries.
Battery percentage on

Battery percentage off

This change allows scaling of the statusbar (the top panel).
As we have to accommodate for a wide variety of devices with different
physical pixel sizes, we need a way to scale the top panel / status bar.
This change introduces a config value (in plasmamobilerc, such as other
shell settings) that controls this size.
For example (plasmamobilerc):
[General]
statusBarScaleFactor=1.5
(Config UI in kcm mobileshell in separate patch)
Signed-off-by: Sebastian Kügler <sebas@kde.org>
This change make Plasma Mobile show multiple batteries in the top panel
in case the system has more than one.
Signed-off-by: Sebastian Kügler <sebas@kde.org>
The eventual goal is to have as few singletons with state as possible in the mobileshell component when it is imported into components such as the lockscreen.
This doesn't fully accomplish it, but moves the audio provider singleton to MobileShellState, which will eventually need to be prevented from importing into non plasmashell processes.
This also disables the sound feedback when changing volume, since it can be a source of lag when showing the applet.
Move from a C++ library + QML plugin to a QML plugin only for simplicity, since the homescreen switching architecture will be done from Plasma, and so use of the shell library only needs to be from QML.