Bug 1032557 - Synchronize logic for collections

https://bugzilla.mozilla.org/show_bug.cgi?id=1032557
In some places I can read icon.detail.type === 'collection' and in other places icon instanceof GaiaGrid.Collection. I think that we should use the same for all of them. From my point of view I prefer type === 'blabla' because I think that is faster