Battery Indicator Support

This release allows adding a battery level indicator to the header or footer.

First, a warning. The settings file has changed significantly. You may want to back up your old settings file in case you want to revert to a previous version. Your old settings will be upgraded to the new format. See the current readme for instructions on the new settings.

The new version allows showing the battery level as either a (configurable) text label, an icon, or both. The icon is not suitable for use in dark mode, as it does not get inverted. When using the Both option, there is a rather sizable gap between the label and icon, which I haven't figured out how to make smaller.

The clock and battery indicator can not share the same location, I tried to allow this but had issues, so it is not supported at this time. It is allowed to use both header and footer simultaneously though.