carousel: hide the container type into slides, current_slide, previous_slide, next_slide. /!\ This commit BREAK the API
carousel: hide the container type into slides, current_slide, previous_slide, next_slide. /!\ This commit BREAK the API

The previous API was bad, the container was exposed to the user: RelativeLayout. We never done this approach in other widget.
This commit give a direct access to the user slide. add/remove/clear widgets are fixed too.

LogicalDash/kivy,thezawad/kivy,jehutting/kivy,kived/kivy,vipulroxx/kivy,arcticshores/kivy,denys-duchier/kivy,eHealthAfrica/kivy,habibmasuro/kivy,rafalo1333/kivy,youprofit/kivy,dirkjot/kivy,viralpandey/kivy,tony/kivy,manashmndl/kivy,denys-duchier/kivy,kivatu/kivy-bak,kived/kivy,wangjun/kivy,niavlys/kivy,yoelk/kivy,manashmndl/kivy,wangjun/kivy,darkopevec/kivy,tony/kivy,Davideddu/kivy-forkedtouch,ernstp/kivy,cbenhagen/kivy,bob-the-hamster/kivy,MiyamotoAkira/kivy,CuriousLearner/kivy,Shyam10/kivy,KeyWeeUsr/kivy,bliz937/kivy,LogicalDash/kivy,Cheaterman/kivy,matham/kivy,KeyWeeUsr/kivy,zennobjects/kivy,xpndlabs/kivy,matham/kivy,JohnHowland/kivy,cbenhagen/kivy,xiaoyanit/kivy,VinGarcia/kivy,iamutkarshtiwari/kivy,janssen/kivy,niavlys/kivy,Shyam10/kivy,niavlys/kivy,dirkjot/kivy,kivy/kivy,rafalo1333/kivy,rnixx/kivy,bob-the-hamster/kivy,vitorio/kivy,Farkal/kivy,jegger/kivy,habibmasuro/kivy,adamkh/kivy,matham/kivy,bhargav2408/kivy,edubrunaldi/kivy,eHealthAfrica/kivy,mSenyor/kivy,mSenyor/kivy,aron-bordin/kivy,gonzafirewall/kivy,vipulroxx/kivy,jffernandez/kivy,el-ethan/kivy,gonzafirewall/kivy,xiaoyanit/kivy,Shyam10/kivy,rnixx/kivy,rnixx/kivy,vipulroxx/kivy,el-ethan/kivy,andnovar/kivy,kivatu/kivy-bak,viralpandey/kivy,Ramalus/kivy,gonzafirewall/kivy,inclement/kivy,Farkal/kivy,janssen/kivy,kivatu/kivy-bak,MiyamotoAkira/kivy,bionoid/kivy,ernstp/kivy,arcticshores/kivy,arcticshores/kivy,VinGarcia/kivy,angryrancor/kivy,jegger/kivy,eHealthAfrica/kivy,ehealthafrica-ci/kivy,ehealthafrica-ci/kivy,vitorio/kivy,bob-the-hamster/kivy,Davideddu/kivy-forkedtouch,bliz937/kivy,bob-the-hamster/kivy,jffernandez/kivy,Cheaterman/kivy,bhargav2408/kivy,kived/kivy,jkankiewicz/kivy,JohnHowland/kivy,autosportlabs/kivy,habibmasuro/kivy,niavlys/kivy,rafalo1333/kivy,Davideddu/kivy-forkedtouch,aron-bordin/kivy,wangjun/kivy,hansent/kivy,arcticshores/kivy,JohnHowland/kivy,manthansharma/kivy,jkankiewicz/kivy,LogicalDash/kivy,Farkal/kivy,yoelk/kivy,denys-duchier/kivy,jkankiewicz/kivy,jffernandez/kivy,inclement/kivy,jegger/kivy,arlowhite/kivy,gonzafirewall/kivy,manashmndl/kivy,arlowhite/kivy,aron-bordin/kivy,angryrancor/kivy,bionoid/kivy,kivy/kivy,CuriousLearner/kivy,eHealthAfrica/kivy,wangjun/kivy,kivy/kivy,adamkh/kivy,Ramalus/kivy,vipulroxx/kivy,jffernandez/kivy,CuriousLearner/kivy,edubrunaldi/kivy,andnovar/kivy,zennobjects/kivy,hansent/kivy,Farkal/kivy,Cheaterman/kivy,Cheaterman/kivy,VinGarcia/kivy,hansent/kivy,MiyamotoAkira/kivy,Ramalus/kivy,akshayaurora/kivy,akshayaurora/kivy,matham/kivy,jehutting/kivy,bliz937/kivy,arlowhite/kivy,autosportlabs/kivy,angryrancor/kivy,cbenhagen/kivy,zennobjects/kivy,janssen/kivy,angryrancor/kivy,el-ethan/kivy,ernstp/kivy,dirkjot/kivy,Davideddu/kivy-forkedtouch,kivatu/kivy-bak,inclement/kivy,viralpandey/kivy,MiyamotoAkira/kivy,adamkh/kivy,jegger/kivy,xpndlabs/kivy,bionoid/kivy,KeyWeeUsr/kivy,xiaoyanit/kivy,manthansharma/kivy,manthansharma/kivy,akshayaurora/kivy,aron-bordin/kivy,hansent/kivy,yoelk/kivy,xpndlabs/kivy,edubrunaldi/kivy,darkopevec/kivy,jkankiewicz/kivy,autosportlabs/kivy,dirkjot/kivy,ehealthafrica-ci/kivy,manthansharma/kivy,yoelk/kivy,iamutkarshtiwari/kivy,zennobjects/kivy,Shyam10/kivy,iamutkarshtiwari/kivy,tony/kivy,youprofit/kivy,youprofit/kivy,bhargav2408/kivy,adamkh/kivy,darkopevec/kivy,ehealthafrica-ci/kivy,ernstp/kivy,janssen/kivy,KeyWeeUsr/kivy,thezawad/kivy,jehutting/kivy,bionoid/kivy,andnovar/kivy,JohnHowland/kivy,mSenyor/kivy,denys-duchier/kivy,LogicalDash/kivy,thezawad/kivy,vitorio/kivy,darkopevec/kivy