better naming for enable Right-To-Left support

Created by: oriSomething

i guess it would be more relevant in BS4, but still, i think we can have better naming so it will be easier to have support when needed to RTL to multi languages site: .pull-left -> .pull-start .pull-right -> .pull-end

same with texts: .text-left -> .text-start .text-right -> .text-end

so if there is .text-left in addition, it will always be aligned to left and won't have unexpected behavior. the reason is when you make RTL support, many times you'll have to support multi languages with both LTR and RTL directions on the same page. so this naming convension, can make it much easier and more clearer for the developer