Major refactor

Removes unused images
Modularizes scss
Creates various partials for backend listings
Merge branch 'dev' into chudix

Conflicts:
	app/controllers/backend_controller.rb
	app/models/user.rb
	app/views/backend/shared/_header.html.erb
adds sourcemaps for sass
Fix session name:
- Fix the name of the variable in session
Branches done:
- User policies are written and checked
Policies de pages y users
Posts policies (not finished)
yeap, i did it. i imported the internet into the project, so what?
Partial commit:
- Pundit
deletes heroku gems
modularizes backend header
Merge branch 'dev' into backend
Changes forms to use admin theme
fixes sign_out error backend

removes various unused js plugins from backend
 some aesthetic changes in backend forms, header and sidebar
templates backend pages index
Merge branch 'dev' into nestier

Conflicts:
	app/controllers/backend/posts_controller.rb
	app/models/post.rb
creando galerias desde post, links rotos, policies post edit comentadas, sin helper para las nuevas galerias