Discover and try out experimental IPFS features

[olizilla]

The IPFS experimental features that are available should be surfaced clearly in Web UI. As a first pass, add them as a list of toggle-able feature switches in the settings tab.

The ux of this won't be great initially, as the user will still have to restart the node, which can't be done in the UI https://github.com/ipfs/interface-ipfs-core/issues/366 We can get the feature in place and then push to make restarting via the API a thing.

As a first pass, this can be hidden for webui use, but visible when used from ipfs-desktop, as there we can do the work to re-start the daemon when the config is changed.

UI proposal from @ericronne

see: ipfs/ipfs-desktop#907 (comment)