Improove multiple keyboard layout support
Improove multiple keyboard layout support

Now, KeyboardLayout widget can work with more than 2 layouts.
Also it fixes the issue #650 (https://github.com/qtile/qtile/issues/650)

add cmd_next_keyboard to keyboardlayout widget

Closes #807

zordsdavini/qtile,de-vri-es/qtile,kynikos/qtile,qtile/qtile,kynikos/qtile,dequis/qtile,flacjacket/qtile,qtile/qtile,tych0/qtile,rxcomm/qtile,frostidaho/qtile,tych0/qtile,jdowner/qtile,zordsdavini/qtile,frostidaho/qtile,ramnes/qtile,himaaaatti/qtile,soulchainer/qtile,rxcomm/qtile,flacjacket/qtile,soulchainer/qtile,himaaaatti/qtile,de-vri-es/qtile,cortesi/qtile,jdowner/qtile,ramnes/qtile,dequis/qtile,cortesi/qtile