Added spacing widget parameter
Added spacing widget parameter

A widget parameter "spacing" is added to TaskList,
which is similar to spacing in GroupBox.
Spacing is used in between two tasks, whereas
margin_x is only applied at the widgets borders.

(Fixes also some minor spelling errors in comments)

kynikos/qtile,cortesi/qtile,ramnes/qtile,kynikos/qtile,soulchainer/qtile,flacjacket/qtile,qtile/qtile,flacjacket/qtile,zordsdavini/qtile,tych0/qtile,qtile/qtile,frostidaho/qtile,cortesi/qtile,soulchainer/qtile,zordsdavini/qtile,tych0/qtile,ramnes/qtile,frostidaho/qtile