Add support to fetch all collectibles

[mariano-aguero]

Connects #317. Connects #318.

Fetch all collectibles and filter the ones that belong to the user. Basic components addition so All Collectibles and My Collectibles can be styled.

Includes

• Fetch all collectibles from opensea and filter them to create allCollectibles and userCollectibles in CollectiblesState. The reducer does not verify if the fetched result represent the same set of collectibles for the all and/or user case, so the data in the store gets overwritten/updated each time.
• Dispatch getAllCollectibles from updateStore thunk.
• Little refactor of components in components/erc721/collectibles to extract common code and ease styling.

Does not include

• Tests (yet).

[unjapones]

Just in case, I spoked with @fvictorio about this PR: we don't have to retrieve the full list of "all" collectibles from opensea because in a real world scenario it implies a lot of data.

There is an interaction with the relayer in the middle that we must perform. We might implement this as a responsability of the gateway, so the code in this PR is stil valid. We'll talk about this tomorrow.

cc @mariano-aguero @Agupane