Fixes #44 . Adds charging icon to charging battery sign

[ghost]

Adds charging battery icon to charging battery size. Fill has been removed leaving only battery and Z badge stroke.

[dnarvaez]

@manuq could you take another look please?

[manuq]

Nice, it works now. The only thing that doesn't work is the fill of the icon when the charge is at 100%. I'll take care of that.

The only other pending thing is remove the monochrome. I sent a new pull request for that.
sugarlabs/sugar#193

Looking at the shell code I found that we also add a warning badge to this button when the battery charge is under _WARN_MIN_PERCENTAGE in extensions/deviceicon/battery.py. Found that the result with these new icons is not worse than before. So let's go with them!

Also noticed that this could have been resolved with a badge, but I'm fine with this solution. The badges are usually be bad placed.

For future, please add a link to the previous pull request when you send a new try. That way we don't lose the previous feedback.

Thanks!