Thanks to Simon for pointing out that a custom menu item would
accomplish what we need and for pointing out the ubuntu app
indicator code that this patch was based on. Additional thanks
need to go to Cody Russell for creating a custom menu slider
widget I could copy.

This way it won't show as two different menu items.

This will consolidate the plugins which can then be renamed.
There's an issue where the mouse grab on the brightness slider
doesn't work, hopefully we can do that without making a custom
popup window. Scrolling on the plugin icon or over the brightness
slider does work.

When the GTK theme changes, resize the panel button and its icon.

When the user selects a device in the battery plugin, the xfpm
settings dialog is activated, the devices tab is brought to focus,
and the device is selected with the details shown.

In the battery plugin, there's a chance that we've filtered out
any devices to display and thus there's no need for the menu
separator.

This way the panel icon will increase with the LXDE icon_size
changes.

Adds support for the battery plugin to be built and used in LXDE
as the system tray icon was removed. Thanks to
https://github.com/nandhp/multiload-nandhp as it was used as a
complete example on how to easily do this. There may be a couple
things that need to be added to make this have the same
functionality as the Xfce plugin.

This makes it really obvious what the menu entry does.

Signed-off-by: Eric Koegel <eric.koegel@gmail.com>

With UPower < .99 this patch will make the battery panel icon
dynamic by displaying the ups or battery device with the highest
percentage. This patch also cleans up a couple small issues with
the last two patches (unused function and variable).

When upower reports unknown there is no useful information for the
device so present that to the user rather than a 0% battery level.

Upower 0.99 supports a composite display device that represents
the state of the computer. When that device type is around we will
use it to determine the panel icon, update the tooltip, and replace
the UP_DEVICE_KIND_LINE_POWER in the menu since it would be redundant.

The left click menu now displays the devices and their status at
the time of the menu's creation.

Rather than using a custom window migrate to custom items in a
GtkMenu. To that end, change from a GtkTreeView to GList internally.

Also put more trace/dbg messages in place so it's easy to track
these issues when upower breaks itself again in the future.

Dynamically changing the icon in the panel itself looks horrible.
Revert and improve it later.