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>
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.