Implement crawler to discover new directors / movies

[booxter]

Right now, the assumption is that I have the full list of directors; I may not (esp. as new directors are born). I should try to find new ones somehow, e.g. by following paths from other crew members (first just other directors, but paths through actors and other staff is probably more promising, since directors don't usually work together; but actors do.)

[booxter]

Exposing more info about other crew members: #23