Add model Dataset and controller Datasets to allow uploading of a dataset for an exising code.

Redesign collapsible group items in all pages.

rails generate model Dataset
rails generate controller Datasets

Model Dataset
t.string :fileanme
t.text :description
t.binary :input
t.binary :output
t.boolean :shareable
t.boolean :editable
t.string :code_id
t.string :username

code.rb
has_many :datasets

datasets.rb
belongs_to :code