Avatar Uploader Improvements

[UncleClapton]

• File input can/should be styled to include a drop zone which responds to a hovering file (again the original file uploader from rollforguild had this, we can pull from that.)
• Crop tool should be hidden until there is a file to crop
• Some "stop points" for rotate should be added (if possible). maybe in 45deg increments each way, perhaps.
• Theming for rc-slider would be a nice-to-have. maybe modeled after the switch input. ditch the side icons, use a single center icon in the slider handle to represent what the slider is for.
• Some changes to submission flow should be considered.
  • After avatar submission has begun, inputs in the modal should be disabled and have a visible change to clearly convey a pending state.
  • If avatar submission fails, controls of the modal should be restored.
• Styling of the avatar on the profile page still needs to be looked at to resolve that "pop-in" layout breaking effect.
• #374
• The selectAvatarByUserId() selector needs to be modified in the following ways
  • user.attributes.image has become user.relationships.avatar. Avatars are now represented as a relationship instead, so we need to check if the relationship exists to determine if the user's avatar should be used.
  • The ID of the avatar resource should be used to cache bust the user's avatar. this should result in the avatar path to appear like: url = `/api/fr/:userId/image?v=${user.relationships.avatar.data.id}\`

[UncleClapton]

@Pero-Moretti note changes on task list. last 2 points are new tasks required. I have also created an "epic" label which has been added to the ticket.