The `N3Store.removeQuads` function silently fails when a quad is not successfully removed

[lecoqlibre]

The N3Store.removeQuads function is not reporting any error when a quad is not successfully removed from the store.

This function just calls the N3Store.removeQuad function without taking into account its return value (true/false).

The N3Store.removeQuads function should throw an error or return something to inform that the operation failed partially or totally.

Maybe this function should check that all the quads exists in the store before to delete them.

[jeswr]

Design settled via #501: removeQuads returns a boolean mirroring removeQuad's contract. Since the return type changes, #501 is labelled semver.major and parked for the next major. Keeping this open until it lands.