Fix wrong package name used on button

In case of conflict, we always keep pkg1, and the question is whether we
remove or keep pkg2.
Use $XDG_CONFIG_HOME instead of $HOME/.config

Likely to not change what's actually used, since it'll default to the same
value should $XDG_CONFIG_HOME not be set, but it's better/proper/allows
user customization.
small confusing-at-first typo in README.md
Merge branch 'patch-1' of https://github.com/emanueLczirai/kalu into next
README: Fix typo
Force icon size on notifications

Since GTK+3.14 the icon size might not be the requested one, so force it
if necessary.
Fix handling clicks on systray icon

The button-press signal wasn't marked handled when it should have.

(Somehow with GTK+3.14 this could lead to middle clicks be processed
twice, though I'm not sure why.)
Remove useless code

Leftover from changes in 7ee7ef77
Add a 16x16 logo for use in menus/buttons

Because GTK+3.14 won't resize the 48x48 one anymore, and gives us extra
large icons on menus/buttons instead.

Fixes #20