Support archives that do not provide a Link memento endpoint

[machawk1]

No such archive currently exists. As discussed in-person, all archives that implement Memento do so with initial support of the Link syntax, which is heavily coupled with Memento.

Other TimeMap formats exist and MemGator writes 'em, but cannot read them. This ticket represents a request for support of MemGator reading other TimeMap formats as its basis...even if the archive does support Link.

It might be helpful to identify what sort of the MemGator logic could be potentially skipped with regard to Link TimeMap parsing if this were implemented.