battery: remove inotify since it doesn't serve much purpose

[czadowanie]

Inotify reports only events that a user-space program triggers through the filesystem API. As a result, it does not
catch remote events that occur on network filesystems. (Applications must fall back to polling the filesystem to catch
such events.) Furthermore, various pseudo-filesystems such as /proc, /sys, and /dev/pts are not monitorable with inotify.
-- inotify(7) manpage

Relevant issue: #2662

This pull request removes inotify integration for the battery module because inotify can't observe changes to the /sys filesystem when made from the kernel-side. This leads to behaviour where the widget only updates on interval or when something else accesses one of the files (eg. cat /sys/class/power_supply/BAT0/uevent). Now this also means that removing/adding new batteries isn't handled properly.

So maybe the actual solution is to copy whatever upower does or just deprecate the battery module?