Issue #698: Add --fullcharge flag to set battery thresholds to max

[lukasnxyz]

This pull request closes Issue #698. It adds a --fullcharge flag to the auto-cpufreq command. For thethinkpad, ideapad_acpi, and ideapad_laptop interfaces, this sets the charge thresholds to 98 and 99 for start and end respectively to allow for a full charge if you are using very low thresholds for battery longevity. The command only runs if default thresholds are set in a config which then will be set back on the next reboot of the laptop.

ps. This is one of my first very first contributions to any open source project, but it's something that I was looking for in a piece of software that I rely on daily. (without auto-cpufreq I wouldn't be able to use my laptop off of a charger at all so thank you for creating this lol) Any feedback about anything being wrong, "unsafe", missing, or things I could improve would be greatly appreciated.