moved create new gadget test to shared example "visually creatable" to keep spec DRY
TDD: added requirement to display only gadgets of current user
gadgets belong to users, user has many gadgets. Updated model specs and factory
only gadgets of current logged in user are listed on gadgets page
added different gadget view modes changing with ajax without whole page reload
added overlay and loading spinner on ajax request
refactored view_modes_selector partial, added gadgets helper