DDBNEXT-768 remove all implementation related to "Favorites" Folder.
DDBNEXT-768 extend favorites concept

   - a folder can have an optional description.
   - remove predefined folder with the name "Favorites"
   - a bookmark can belong to more than one folder, by default to none( [] )
DDBNEXT-768: add findFavoriteById

  given a favorite/bookmark ID, it return the favorite/bookmark object.
DDBNEXT-768: can only add max. one bookmark with the same item ID
DDBNEXT-768: save favorites to multiple folders.

DDBNEXT-768: add copy favorites method.

    The return carriage is important after each line. See Also: [_bulk endopint
    fails when on single index](http://elasticsearch-users.115913.n3.nabble.com/bulk-endopint-fails-when-on-single-index-td4030411.html)
DDBNEXT-768: copy more than one favorites to more than one folders.
DDBNEXT-768: update folders' title or description
DDBNEXT-768: add remove favorites from a folder.

    When the user remove favorite(s) from a folder, the issue DDBNEXT-727 will
    use the method implemented in this commit.
DDBNEXT-768: refactor
DDBNEXT-768: add method delete folder.
DDBNEXT-768: fix test
Merge branch 'feature/DDBNEXT-768' into feature/DDBNEXT-772
DDBNEXT-772: add delete all user favorites.
Merge branch 'feature/DDBNEXT-772' into develop

Conflicts:
	test/integration/de/ddb/next/BookmarkServiceIntegrationTests.groovy
Merge branch 'develop' of https://github.com/Deutsche-Digitale-Bibliothek/ddb-next into develop