Support importing/configuring with standard archival specifications

[machawk1]

• http://git.io/archives (json used by MemGator)
• WAM (yaml used/created by WebRecorder)
• Archive Registry (xml by LANL) for its Memento aggregator (assumably).

See more information advocating a list in @shawnmjones's Mementos in the Raw post.

See also #258 #236 #184.