doc: added constructor example to uix/layout.py
doc: added constructor example to uix/layout.py

cbenhagen/kivy,matham/kivy,darkopevec/kivy,bliz937/kivy,yoelk/kivy,bionoid/kivy,akshayaurora/kivy,tony/kivy,mSenyor/kivy,youprofit/kivy,el-ethan/kivy,rnixx/kivy,matham/kivy,iamutkarshtiwari/kivy,inclement/kivy,arlowhite/kivy,Ramalus/kivy,Cheaterman/kivy,aron-bordin/kivy,akshayaurora/kivy,Cheaterman/kivy,andnovar/kivy,arlowhite/kivy,el-ethan/kivy,rafalo1333/kivy,viralpandey/kivy,bionoid/kivy,jehutting/kivy,yoelk/kivy,manashmndl/kivy,andnovar/kivy,MiyamotoAkira/kivy,MiyamotoAkira/kivy,mSenyor/kivy,LogicalDash/kivy,inclement/kivy,jffernandez/kivy,kived/kivy,habibmasuro/kivy,jffernandez/kivy,VinGarcia/kivy,KeyWeeUsr/kivy,inclement/kivy,andnovar/kivy,manthansharma/kivy,xpndlabs/kivy,ernstp/kivy,edubrunaldi/kivy,kivy/kivy,xpndlabs/kivy,autosportlabs/kivy,yoelk/kivy,youprofit/kivy,CuriousLearner/kivy,CuriousLearner/kivy,kived/kivy,LogicalDash/kivy,ernstp/kivy,autosportlabs/kivy,edubrunaldi/kivy,vitorio/kivy,Shyam10/kivy,manthansharma/kivy,KeyWeeUsr/kivy,bionoid/kivy,matham/kivy,jehutting/kivy,aron-bordin/kivy,jegger/kivy,cbenhagen/kivy,iamutkarshtiwari/kivy,thezawad/kivy,jegger/kivy,jkankiewicz/kivy,el-ethan/kivy,rnixx/kivy,edubrunaldi/kivy,bhargav2408/kivy,KeyWeeUsr/kivy,manthansharma/kivy,arlowhite/kivy,LogicalDash/kivy,Shyam10/kivy,VinGarcia/kivy,tony/kivy,aron-bordin/kivy,tony/kivy,thezawad/kivy,cbenhagen/kivy,xiaoyanit/kivy,Ramalus/kivy,ernstp/kivy,viralpandey/kivy,jegger/kivy,rafalo1333/kivy,matham/kivy,Shyam10/kivy,rnixx/kivy,youprofit/kivy,manthansharma/kivy,kivy/kivy,manashmndl/kivy,VinGarcia/kivy,bhargav2408/kivy,kived/kivy,darkopevec/kivy,vitorio/kivy,bliz937/kivy,darkopevec/kivy,janssen/kivy,jegger/kivy,MiyamotoAkira/kivy,janssen/kivy,iamutkarshtiwari/kivy,jffernandez/kivy,xiaoyanit/kivy,janssen/kivy,mSenyor/kivy,akshayaurora/kivy,yoelk/kivy,jkankiewicz/kivy,bliz937/kivy,manashmndl/kivy,KeyWeeUsr/kivy,Ramalus/kivy,kivy/kivy,LogicalDash/kivy,autosportlabs/kivy,ernstp/kivy,Cheaterman/kivy,Shyam10/kivy,janssen/kivy,habibmasuro/kivy,bhargav2408/kivy,Cheaterman/kivy,habibmasuro/kivy,MiyamotoAkira/kivy,viralpandey/kivy,jkankiewicz/kivy,aron-bordin/kivy,xpndlabs/kivy,rafalo1333/kivy,vitorio/kivy,jehutting/kivy,CuriousLearner/kivy,jffernandez/kivy,darkopevec/kivy,xiaoyanit/kivy,jkankiewicz/kivy,thezawad/kivy,bionoid/kivy