Allow overriding charge limit and charge full

[JohnAZoidberg]

TODO:

• Allow overriding charge limit
• Add removing charge limits
• Add (UEFI) docs

[brlin-tw]

I've tested the branch and the behavior is somewhat different than what I expected:

• After running the command the system does charge the battery to 100%, however after unplugging the power and replugging it, it seems that the system still tries to charge the battery.
• The system also tries to charge the battery past the previously set charge limit after the battery charge has fallen under the previously set charge limit.

I expect the charge limit will be restored after the power source is disconnected after the battery capacity has reached 100%, however, it seems that to restore the charge limit settings one has to:

• Run the --charge-limit command to manually set the charge limit back.
• Reboot the system so that the firmware will reset the settings.

I would assume that the behavior I imagined might require implementation in the EC firmware as well and is out-of-scope of this project, though.

[JohnAZoidberg]

Thanks for testing! I have to think about that for a bit.
At the very least it's worth documenting how exactly it behaves.