Discussion#show - refactoring
Discussion#create - remove format js
Discussion#create - change redirect_to in format html
Project#show view - change link_to add discussion
Discussion#show view - refactoring link_to edit
Discussion#show view - add backlink
Discussion#edit view - change Cancel link
Disussion#edit view - add class 'paper'
Discussion#new view - change backlink
Discussion#new view - add class 'paper'
Discussion#_form view - fix bug with url