Tweak notification text to be more user-friendly and less jargonistic
Some of the notification labels suffered a bit from excessive wordiness, repetition, and jargon. This commit cleans them up to be more HIG-compliant by rephrasing some things:
- Don't repeat the title in the body text.
- Minimize or eliminate the words "you" and "your", which sound awkward or accusatory in English.
- Use the term "system" instead of "computer", because not all systems are computers (e.g. phones using PlaMo have Powerdevil).
- Use the term "power cord" instead of "AC adapter", because it's more common and also more accurate since not all power cords do electrical rectification (e.g. a USB charger plugged into a car's 12-volt socket).