refactor(selection): moved selection views in own folder
refactor(selection): select button becomes extra view class
refactor: cleanup in slider and cockpit
feat(selection): toggle button extends indicator
refactor(selection): introducing an (abstract) base class for selection view components
feat(style): button states
feat(selection): added select-button to cockpit
feat(gallery-model): data-src attrib defines data source for GalleryModel
feat(selection): GalleryModel gets id = md5 hash of src attribute, extra Selection for every Gallery
fix(cockpit): change in styles: cockpit always full width, image-meta: text-overflow:ellipsis
feat(styles): demo-page nicer on phones
feat(selection): selection key => possibility of 1 selection for various galleries
refactor: remove superfluos methods
feat(selection): selection as a source for a gallery

syntax change for gallery data attributes: data-gal prefix
refactor(gallery.factory): cleanup and methods extracted
feat(selection.gallery.model): selection is only initialized once
feat(app): give gallery DOM element css class, when the gallery is empty
refactor(emptyness): react on removing photos from selection/gallery => mark empty
feat(app): register onInit(app, galleryModel) callback on app
feat(app): add metadata to gallery model just as we can add it to images