refactor(users): update user list to follow new design

- Add global styles for preview layout
- Refactor archive to work with new layout style
- Add new layout styles to users screen
- Replace user details slide-pane with static pane
- Replace user table with user list
- Action buttons changes
- Create users profile page
  - Keep quick view/edit on user list screen
  - Add full profile view/edit
- Styling improvements
  - Add SVG icons to user list page
  - Fix avatar size on profile page
  - Change avatar on activity log, and top bar to be rounded
- Users list > table view refactoring
- Remove ability to switch on/off columns in users list
- Remove UserSettings service
- Remove service for handling user settings in local storage
- Users module > merge directives
- Merge all separate directive files into one
- Move sdUserName directive to common directives file

close #147
refactor(datetime): add superdesk.datetime module with reldate

reldate was part of items module, now it will be in core