Clean images controller, user model, form, routes

Take out the instance @gallery that we didn't need,
define a relationship in the image model that lets us
join images and galleries tables.

Routes were re-organized to reflect changes in images controller,
same with the galleries show page.
Fix action objects in edit and new
Add image shoe page
Add comments to pictures
Clean controllers, add scope for ordering comments

Clean the images and comments controller to go with best practices
Add scope in comment model that orders comments by time created.
Form for new groups correctly displays
Users can create groups, and view list of groups
Add errors to form, and uniqueness validation
Update images assigning to groups
Refactor routes to singular
Destroy groups
Add image likes, user follows, user dashboard
Add tags to images and display on gallery show
Change tags table column name
Add tags to images, show all tagged images
Add tags, remove tags, tags on show page